what is your tank temp and how often do u change water? if the discus
are not themselves, raising the tank temp to 30C and daily wc (or
increase your wc regime) is a good start and safe to do...
(30c may be high for your other fish)

feed more, more wc, feed less, less wc. I tends to feed them twice to
3 times a day when they are ~2". (but when in doubt, like what is
happening, feed less...)

what other fish are in the tank?