Your plants look wonderful! If you have a fan blowing directly at them it will cause leaf twisting. You can point fans at wall and let it reflect. Or it is due to fluctuations in PH levels. Happy Growing and keep up the good work!
yeah, here you had this N toxicity already, plus as mentioned, could be wind damage added to some state of leaves.
You should slow down all feed and start watering them right in right amounts, with runoffs, without leaving dry pockets inside of pot and water when pots are dry and easy to lift, in your case some top lair can dry out, but plants stunt and wont drink, lifting is very important.
those meters sometimes brake from smallest drop, invest 5-8 £ into buying aqua drops and recheck your meter after calibration ....
i had like 30 of those yellows in my life , till i finally went to BlueLab ...
Both need regular calibrations, just one last long and works.