Maybe you are just taking too much and that a lower dose will be a helpful part of your combo of supplements over the long term.

Learn about catecholamine neutotransmitters, especially dopamine and norepinephrine/adrenaline.

High dopamine is associated with schizophrenia.

High norep is associated with panic attacks, intense personality, etc.

Ever try a little lithium orotate. You might try one 5mg capsule on day one to see if you feel more "chilled out." However after that 1 or 2mg per day might be enough, maybe even less.

In the heavy metal detox groups we often see very low Li in hair in people with an "intense" personality. That was my experience. I'm not suggesting it is a cure-all but is something to investigate if intense personality is in an issue. There are 1000+ tests + symptoms here.
http://livingnetwork.co.za/chelationnetwork/hairtest/hairtest3/

Glutamine and the related amino acid GABA can help to produce a calm altertness. Again I would not expect them to be a magical fix-all for most people but might be a nice part of your combo.

Magnesium is a must-try for a more calm disposition.

If you've completely stopped taking THC after many months/years of taking it - you'll experience a dullness due to the brain receptors not getting their 'fix'.

As i explained in a previous post, neurotransmitter receptors will downregulate when flooded with what the brain considers to be too much dopamine/serotonin etc. It'll automatically make the receptors less responsive to the chemical hit.

With daily THC use, this happens, and therefore people end up taking THC more, just like those on SSRI's gradually need to constantly increase the dose or change to another SSRI once the receptors become less sensitive.

The choice one has is to take some other form of serotonin/dopamine - however, that's not a cure - it won't cure receptor down-regulation, it'll only perpetuate it.

The best route is always the hardest. It's akin to cold turkey.
Don't take anything to drown those receptors - so they can begin to become more sensitive once again to lower levels of neurotransmitters.
This takes months. I've done it - it's a very rough road - and requires an inner strength to carry on the path.

If it's impossible, then take just small doses of 5HTP or GABA or whatever works...just tiny doses. Try to work towards taking less and less to wean the brain off of such high doses.
In this way the receptors can have the opportunity to reset their sensitivity.

One thing which really helped my 'dull' feeling was being outside...fresh air, gardening, moving around. Nothing hugely strenuous, but i kept moving and ended up spending hours outside each day. Luckily i work outside so am used to it - i really hate being inside a central heated room, it feels too stuffy, hot and claustrophobic to me.

When recovering from anything, it's natural to hit some troughs that make us wonder if we'll ever heal.
They are temporary, and it's wise to remember the body is always trying to heal. We have to become the facilitator to help it on it's journey. If that means cutting something out which has completely screwed up out bio-chemistry - it must be done, even if it lands you in a hole for a while.

It's okay to go into the territory of feeling utterly crap. It won't kill us. But each of us knows our limits for that place! So also be kind to yourself and if GABA or glutamine or whatever works does help, use it, wisely.

I have a friend who is battling THC addiction and is similarly very dull, de-motivated, depressed when without the 'hit' that THC, CBD combo gives. As soon as they have a hit their personality lights up, they are more talkative, more active, more charismatic, think clearer. It's a powerful effect and is addictive in that sense.

If you were to use THC CBD combo - i would suggest low dose of both at exactly the same percentage...i.e.4% of each. If you find anxiety and paranoia an issue then find a strain which is 4% CBD and 1-2% THC - they do exist - that would keep you calm and more relaxed without feeling so dull.

Yet as i suggest above, keep in mind that your receptors are in a state of flux - so have a dose which does the job but is not a 'hit'....and try to then reduce that dose over the course of months/weeks to help the receptors gain their natural sensitivity.

The info regarding the endocannabinoid system and it's interraction with the endocrine system is currently being studied...not much is known, yet is suggested they inter-play.
There are many opinions online about this - yet very few studies are often cited, and are soley the opinion of the author without evidence to back that opinion up.
Endocannabinoids are relatively new to human awareness and so it's wise to look for independent studies on the subject to fully gauge an idea of the impact of heavy endocannabinoid use.

Personally, i know light users of THC who are perfectly healthy.
Some people have said to me the same of light heroin users, who hold down a job, have a healthy family and life.

It seems heavy use of anything - even Sugar and caffeine, is destructive to balanced bio-chemistry...and therefore affects out health and life negatively.
I guess the old saying 'everything in moderation' really is a golden rule to follow.

One could spend soooo much money on diagnostics to find out the imbalances...and sometimes i think its a very good idea if you already have an idea what's wrong...yet the very start point is to cut out excesses...not just diet - but life too. Excess sugar, caffeine, protein, carbs, stress, sex, worry, alcohol, junk food, internet, procrastination etc etc anything that goes into or the body is subjected to excessively eventually creates an imbalance.
Even excess oxygen and water isn't good for us!

Many nutritional/mineral imbalances leads the body into a state of flux and fatigue eventually. Primarily gut health and a balanced diet and/or excellent quality supplements should show benefits.
However, there's no point in relying on supplements to heal if everything else in life is excessive/stressful/imbalanced.
Progress isn't overnight, it's a path, yet the horizon keeps changing even at times when we feel 'stuck'.

Feeling dull after feeling so wired for so long, although not ideal, might be what your system needs right now. Sometimes we have to ride the wave, not medicate it. If it becomes continuous for weeks on end, then it probably is a result of lack of THC to 'wire' you up...if THC is the one thing you know makes you feel wired and awake.