Pics will help us determine the problem. What are you feeding themm how much? and how often? How old are they? Ph?Etc and we can help i had issues with mine and they are fine now once i figured the problem.
Overwatering, underwatering, not enough nutes. All depends. Lack of nutrients could cause them to turn yellow lack of water they can droop down. But can also be nute lock and they are too deprived.