Originally Posted by
snoopodus
Welcome to simply,
1, Ok part of the problem is that you really need to quarantine new fish when you get them you said you had the first set of discus for about a month and a couple of weeks ago you bought two more discus and put them with your first set.
2, But since they have been in the tank for a couple of weeks together what ever is wrong with the two new discus has already been exposed to the first discus.
3, It could be many things maybe the other discus in the tank are bullying the new one during feeding time or it could be parasites.
4, How is there poo is it black clear stringy or Are they just not eating
5, I would start by doing a large water change about 80% with aged aerated water at the same temp. And see what that does sometimes that's all it takes to stimulate them to eat, also try moving things around in your tank (rock, plants etc...) what that does is make the discus start over with territories in the tank and should help with bullying........hope it helps