Discus spitting out food is a pretty sure sign of internal parasites. The shape that your discus are in, it would be hard to believe they don't have parasites, just very, very common when purchasing discus from LFS. Right now the next step I would take would be to treat them for internal parasites with Metronidazole (Metro) which treats internal flagellates, the most common internal ailment in discus.
Some amount of bullying amongst discus juvies is normal. It's part of them growing up. Every once in a while you get a real tyrant of a discus that barely lets anyone on the tank move.....I have had them and rehomed them. The bigger the discus group, the more spread out the aggression is so that one particular fish isn't getting picked on all the time. If one discus gets singled out and bullied relentlessly, they often stress themselves to death.
Hi there! joining this thread late in the game so forgive me if some has been repeated.
I am a re-born discus owner (had some over 25yrs ago) & I made quite a few mistakes that I hope I can share so others will not make the same.
1. QT all fish - trust no one, not even your own cross tanks!
2. b-4 buying or trying something new or changing your maintenance or whatever, ask away on these forums cuz there are many many experts/pros out here to help us & to minimize our mistakes & to help us thru our problems
3. your discus purchase I feel was not a good one. the LFS are not really good discus keepers, they are sellers no matter what. emaciated, oval shaped, dark. next time when you want to buy ask the forum members. I would say buy from reputable sellers - & you get what you pay for.
4. I agree on meds for parasites/worms. I had them went thru a tough time but finally got thru it (loss 1 of 15 juvies).
5. W/C frequently (espec. with gravel substrate) I have a bare bottom with 3 cosmo glass graveled cups of plants which in itself collects a lot of debris so imagine a tank full of gravel how much grit is collected/deposited. bare bottom not so pretty but with my cosmos & driftwood better than nothing but also easier to maintain. & no gravel vac! tho I still vac the heavier poopy doop!
6. overfeeding & less w/c leads to planaria also, which I experienced also.
7. discus need to be in groups, many recommend min. 4-5. I bought 15 & mine all peck each other - no one is overly dominant but even the smallest juvie dukes it out with the bigger boys! but I didn't mix any other fish, not even pleco or catfish. just a nice tank of discus. so in-fighting is natural more so with less discus.
8. don't recommend canisters (espec. fluvals) as they have tendency to back wash cruc (stuck in the coiled tubing) + they cost way too much $$$. I recommend AC's (110 or min. 70).
9.
www.kensfish.com one of the best highly recommended suppliers (espec his foods) + prices are excellent & shipping costs very reasonable
10. good luck & enjoy!
forgive me if many of this has been said - I wanted to share my probs & how I was helped by other members.