"Her ADHD is through the roof lately for some reason."
Consuming all that milk she will to me be clearly magnesium deficient. Magnesium is very difficult to get enough of even without the milk (Calc is an antagonist to mag) In what form is the magnesium you give her ?
just beware that vit B is an important part of the supplements I recommend; as mag/zn/Fe are dependent of it for uptake (and again, almost impossible to get enough from good organic food, I have tried!)
The ADHD cases I have worked with; cut most milk, but they use cream and butter in cooking (to get the fat)
If she is celiac, absorbing minerals may be an issue; I would add some digestive enzymes for a few weeks, see if there is an improvement.
Selenium; I give approx 100 mcg per 2 drops of Lugols (5%)
I would try for a month or two a higher amount of iodine; like 4-10 drops per day, increase real salt.
The RO / distilled water needs minerals in it - hopefully some others chime in here, as I am not familiar with it.