I would say up pot them all. JMO but if they have been in those pots for a month then you might have roots exposed in the bottom of the container and when you feed them those exposed roots catch alot of the nutes from the water in the catch tray. dont know if its right but sounds good while...
I would not change a thing yet. some times they can slow on nute intake when they change from veg to flower.
I put the links to some books here. https://www.rollitup.org/Journal/mike4c4.764086/ Hope they help.
The first pic is showing heat stress and i would say that when your spraying the plants when the lights on are burning the leaves causing the spots. water drops under hot lights act like a magnifying glass.
When i clone in cups i only mist once put the lid on and dont open for 3 days then remove the lid dont put it back on and mist once a day, you dont want them too wet and mine root in 12 to16 days with that strain.