Like the other poster said, I think you are really toxic and that is why your tongue is showing the white plaque known as thrush. Bottled spring water, Reverse Osmosis or distilled is usually the preference for fasting with distilled seeming to be favored on some boards. You tongue is holding on to the color particles from the food because the thrush is acting like a canvas to whatever you put into your mouth.
You water purifier unit sounds like it has seen better days. Personally my belief is if you cannot remove the filter or clean out the water purifier in some way then the contaminants are blocked the filtering mechanism after a certain period of time.
There are many alternatives to water purification. The simplest is brita pitcher or bottle water. Among the best would be a multi stage purification system with replaceable filters ie reverse osmosis or your own distiller that you can clean.
Any source is probably better than tap water which has from time to time been reported to have 350 chemicals or more in it including components of fuel and residue of pharmaceutical drugs that get into the waste removal system.
I know it is really tough, but you have to be strong and be an advocate for yourself and seek out knowledge and ideas that will help you. In the end only you can make the best choices for you. If you look back on my own postings you will see I have had a difficult path as well.
Having done two lengthy water fasts. I can tell you the second was easier than the first ( you become less toxic and healthier) for three reasons the first helped detox me some, my diet was healthier and I did a bowel detox before going into the second one.
If you have never fasted try short fasting periods like 24 hours or 3 days or 7 days with healthy eating in between mainly fruits vegetables multigrains no refined products canned foods or drinks. fruit and vegetable juicing will help you detox but at a slower rate. If you may have a fungal infection some people report that using more vegetable juices is better so as not to feed the fungus.
on your Water Fast drink according to thirst and only bottled water or purified water no tap if you can avoid it.
You will get better. How much you do for yourself depends on the progress you make. Help yourself and get some sound knowledge. Ask research go through old posts and the like. It takes time to heal and to detox from our toxic environments and the stuff we put in ourselves.