It could be more than one thing - Im pretty sure it will be a temperature problem, what is your grow room temperature? Also what is the level of the ph in your soil? How old are the plants? Growth could be stunted so we really need to know everything about your setup and plants quickly so we can make a diagnoses before it is too late. Also: Picture would help. Peace
Temps are 30 or more during the day and around 20degrees at night its and outdoor grow they are 2 months 3 weeks old no ph tester at the moment and cant buy one because where i live in europe they cost a lot will take pictures later when the sun goes down