Looks to me like aPH problem
your Ph is to high,
and that looks like airon defiency
seveeral things lead to this, stressing envoirement, wrong nutes, overwatering etc, look for the roots
i would give them aflush, check ph before your feedings ( check the solution)
i let you alink for the remedies
https://www.growweedeasy.com/cannabis-plant-problems/iron-deficiency