I personally would get some aeration going in there. If what you say about extra fish food going uneaten on the bottom is true, you could have rotting fish food down there causing some water quality issues. I am thinking of the typical aquarium ownder dumping in too much food to the point the fish die from low DO and high nitrates (nitrites? I can never keep them straight)
An aquarium water test kit should work if this problem is true. Take samples down near where the food sinks.
Sorry to hear of your health issues, and hoping some new therapies will become available to help you out.
