I would try not adding food for a little while and see if the ammonia/nitrItes drop down.
FWIW prime and other ammonia locka and dechlorinators will lock up the ammonia but normal test kits like the api ammonia test still reads ammonia. The danger is you read ammonia, add more chemicals and read ammonia etc etc etc. All the while that first dose may have totally locked up the ammonia and the following doses were unnecessary.
But one side effect is the chemicals also lock up oxygen and you can actually suffocate the fish which has the same symptoms as ammonia.
so you could try
1) adding some fast growing plants like Anacharis
. (or perhaps you plants are just fine)
2) stop adding food
3) stop doing water changes
4) stop adding the chemicals.
then see if ammonia and nitrItes drop in 3-4 days.
But that's just my suggestion which is worth at most.