Yellowing on Plants

Your plants are huge for the pot size... Aim for at very least 7l pots if the plants genetics won't let them grow very large, 15-20l ideally. The roots are probably blocking one another and not letting your plant eat properly.

The issue - They are growing in totally inadequate tiny cups in exhausted soil mix. The solution - Transplant them into decent sized pots, 15 litres and up, with fresh soil and they will recover and start growing properly. Basically - You can't grow an elephant in a canary cage! The yellowing is a sign of the deficiency of all 3 major nutrients and is something not related to either calcium or magnesium, which your plants do not really need in greater quantities until they are flowering or unless/when growing with pure coco coir. Hope this helps, Organoman.