discus hiding/turning dark/ not eating help!!!!

[ziggypop]

75 gal planted
ph 6.4-6.9
co2 injected
ammonia .25 and nitrie undetectable
nitrate 5ppm before wc
wc once every 3rd day about 35%-45%
2-200 watt heaters set at 84 F
fluval 406 can filter with quilt batting bottom biomax 2nd bio balls 3rd and mix of carbon and purigen in top
tank is fully cycled and stable
Before i started keeping discus i had the tank running with some cory cats and guppies for about 2-3 months to fully cycle media before removing and adding discus to aquarium.

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Help!! the 4 discus in the top corner are my concerns. I unfortunately lost one of the juvinilles in the tank today. my concerns are that the 4 there havnt been eating in a few days the blues are turning dark. Also i have seen a couple fish with white almost stringy poop. I do a 35% water change at least every three days with declorinated water from tap at 7.0 which i add a tiny bit of acid buffer to. the ammonia was reading 0 the other day and i suspect the ammonia in tank is just from decomposing fish which should lesson with the water change im doing today. the light is on a "mostly sunny cycle" and gradually gets a little dark then light again(not drastically) i feed a mix of bloodworms frozen dried flake and discus pellets which i rotate every feeding. They usually come to top of tank and eat readily. i dont know if this is from hard ness which i didnt have co2 running for a couple of days. the water quality which should be pretty ideal temp is stable. Only thing i can think is i added 3 then 4 and im wondering if they got something (didnt have a quarintine up yet) in the adding. Please help i will gladly answer any questions also the 2 lighter color fish are the "bullies of the tank and still come up eat regulary and seem to get along well. about a week ago all the fish were out swimming happily together

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This was about a week ago

[Surf&turf]

How long has the tank been running? Ammonia at .25 is not good, are you using any thing to help reduce the ammonia?

[ziggypop]

tank has been running a good 5-6 months completely cycled but i had 0 ammonia the other day but imediately checked water once i saw dead fish dont have any ammonia reducers other than my "Aquasafe declorinator going to pick up prime tomorrow and start using that instead
they were healthy and loving life but then nitrates went a little high at 10 ppm so i did a large water change about 50% 2 days later and dead fish the others are not looking very healthy and i have ammonia for some reason

[Shaun's Discus]

Somewhere along the line when you did that large 50% w/c you may have shocked your cycle and killed off some beneficial bacteria. Don't waste your time and money on anything else other than Prime or Safe and always pretreat ur water before putting into tank. I've seen so many people on youtube dumping water into the tank then adding prime, IMO you may get away with this sometimes but it only take that ONE time when some tap water nasties get to your b/b and boom, a mini spike and some Nh3, yes .25 will do your discus harm. Do another w/c when you get your prime ASAP Maybe a good idea to grab a bottle of Stability as well and add some of that along with the prime.

[ziggypop]

okay i did a 35% water change like 20 mins ago and used just the declorinator i will do another 35% tomorrow with prime and see where we get i always pretreat let sit for about 5-10 mins then pump into tank. also the ones that were going black have been since before big WC and have started to seem a little restless I know its just keep giving them clean water and raise the tank temp gradually just worried dont like losing fish : (

[eros111]

Where did the new fish come from if you did not quarantine them - maybe you have introduced something by not doing the quarantine. I would stop feeding the bloodworm - I hate that stuff - full of bad bacteria - I have had serious issuuse with bloodworm once and killed some fish. The white stringy poop is an indication of something going on in their gut - I would treat all of the fish for worms/internal parasites and the white poop should clear up. Damn I'm sorry you are having issues with your fish.

[Ryan925]

Somewhere along the line when you did that large 50% w/c you may have shocked your cycle and killed off some beneficial bacteria. Don't waste your time and money on anything else other than Prime or Safe and always pretreat ur water before putting into tank. I've seen so many people on youtube dumping water into the tank then adding prime, IMO you may get away with this sometimes but it only take that ONE time when some tap water nasties get to your b/b and boom, a mini spike and some Nh3, yes .25 will do your discus harm. Do another w/c when you get your prime ASAP Maybe a good idea to grab a bottle of Stability as well and add some of that along with the prime.

I fill straight from tap into tank. No pretreat no issues. From what I gather most people that age water do not pretreat either. Actually they prefer to dose the tank rather than dose the barrel to prevent buildup in the barrel

I would go your wcs to daily and see what happens. Lots of fresh clean water is always a good start and ditch the acid buffer