I got a better photo: http://imageshack.com/a/img923/6684/komrpz.jpg
Forgot to add that the discus is eating a little bit more than before, but I think it is connected to the hex treatment.
Regarding the massive die-off I had on the 4th of introducing new fish - is it possible that the fish died because of overeating or bad food?
All the fish that died were the ones who liked to eat the most.
3 hours before dying they were all normal and eating. Unfortunately I left my home for these 3 hours and they were dead.
It seems weird that there was a loss in all the species at the same time (1 discus, 4 congo tetras and 3 SAEs). SAE's should be more hardy.
Temp was 28 C then and parameters normal.
Even if there was ammonia spike, wouldn't it have killed all fish or only discus (most sensitive)?
Thank You