"My brother says that when he wakes up he feels no brain fog but when he's on his feet as the day goes on it comes back."

Sounds like it could be hypoglycemia, dehydration, or perhaps a deficiency of sodium or potassium. In this hot weather, it is important to not just drink extra water, but also to take in extra sodium and potassium, as well as other minerals.

Is he eating well? Getting enough protein, vitamins, and minerals?

"He's taking Chelorex and it makes his head feel heavy like a brick "

Why use chelorex? Have you looked at its ingredients?

Serving Size: 18 Caplets
Servings per Container: 30



Vitamin C (as ascorbic acid) 1,000 mg 1,667%
Vitamin E (as d-alpha tocopheryl succinate) 400 IU 1,333%
Magnesium (as magnesium aspartate) 500 mg 125%
Zinc (as zinc citrate) 20 mg 133%
Selenium (as sodium selenite) 200 mcg 286%

Chelorex? Proprietary Blend 6.9 g *
MSM (Methylsufonylmenthane), Cracked Cell Chlorella, N-Acetyl-L-Cysteine, L-Glutamine, Taurine, Cilantro Leaf Extract and Alpha-Lipoic Acid.

http://www.detoxhealth.com/chelorexingredients.html

ALA needs to be taken every 3 hours to minimize redistribution.
Is he taking 18 capsules a day? It looks like 18 capsules costs around $3? Buying these ingredients separately allows more control over dosages, and will probably cost less.