Perhaps theres a language barrier but let me make a few corrections first.
It's
bloat not blout, which could be confused with clout (fish medicine)
second, Nimbochromis venustus are Haplochromines not Mbuna.
you said "upper bottom".....

uhh

which is it? lol
unless you feeding straight blood worms 3 times a day, basicly gut loading them I dont see how you're going to bloat them as Haps require protiens along with veggies in their diets unlike most mbuna which require veggies only.
also you mentioned they've looked like this "for a long time" ...bloat would have killed them by now.
how often do you feed and WHAT are you feeding?
how many do you have and what size tank are they in?

catfish pic!!!