What substrate do you have? Are you experiencing plant death? How often to you prune? Ammonia is a product of decay, you seem to be experiencing a large amount of biologic breakdown (decay) be it overfeeding, lack of bio-bacteria, substrate or plants decay, etc. What is your KH?
X2Seems you have several things to fix.
1) Actinic and 10k lights are just about useless with live plants. You need to be in the range of x235k-65k
2) With discus you dont need to change a lot of water you HAVE too, Juvies need good clean water or you will have a slurry of trouble and stunted discus. Im talking large wc's 1-3 x's a week
3) I dont think you feed near enough for that stock list. I had 6 2-3" discus and they would plow through 3+ cubes of blood worms a day
4) You need to clean your filters more than you are.
5) gravel/sand vac every wc and clean your filters atlest every 2 weeks with discus. I personally would do it every week.