Goldfish trauma?

I lost a common goldfish to high nitrates a year ago. Since then I've been trying to get the nitrates under control (unsuccessfully). I have 2 goldfish, a 5 inch common and a 3 inch fantail and they were in a 10 gallon tank. They both just sat around on the bottom of the tank most of the time and the common goldfish has weird lumps on his sides. No amount of water changes would bring the nitrates down so this week I bought a 30 gallon tank for them. I thought would help and that they would perk up but they still sit around on the bottom. There is a little ammonia in the water right now (about .25-.5) but all of the other parameters are great. Are these little guys just permanently brain damaged from sitting in nitrates for a year?