I hope you take this in the right context Niko as it is truly meant in the bests interests..
some of those fry are never going to make their fiull potential and i would place a bet that they will not reach a decent size. body shape and eye size are always a good indicator.
how many times a day are you feeding your fry? (small discus need at least 5 times a day due to their high metabolism)
i have attached a pics for a good size and shape indicator for fry at around the age im guessing your fish are at..
high protein diets and spotless water quality are an absolute must for fry.. bare bottom tanks are quiet literally a must to get your babies growing to a size that discus should be... 17-20 cm is a good size to aim for in an adult..
hope you find this useful
Adam
