How old are they now?
When was the last time you transplanted them?

They look quite big for the pot but also at the same time - just in general look small.
What strain is it? If you can lift it out of the pot and look at the soil... see if there are a lot of roots growing around the soil, that may be the problem.
Give me some more info and I'll try to help you out better.
:hippy::jointsmile:

Ps. Your lights also look pretty close to the girls. Use the 'hand method' to test and see if your lights are too close or not.