veggienft is correct - the Adderall is the most likely culprit. Hallucinations are not a super comment side effect with stimulants, but they are well documented. You should probably see the psychiatrist and ask about decreasing the dose to see if that helps with the problem. Alternatively, you could talk about switching to a different stimulant like Concerta or Ritalin because each drug has different side effect profiles.

Gluten free/casein free diets have no research supporting reduced psychosis. They are really only helpful if your child has a documented gluten allergy.