Why are leaves turning yellow?!?!

She is hungry, My guess is you have a nuturent(salt) buildup causing a lockout. Could also be your PH is out of range but soil is very forgiving as long as your putting the correct PH into the soil. Just looking at your pictures Im guessing the cause of the buildup is from 2 things. 1. Not watering/feeding with runoff( 1/3 should runoff). So if you water 3L of water you should have 1L drip out the bottom. 2. Letting the plant sit in runoff. You should elevate your potters a bit so they don't sit in the runoff because this will cause a salt buildup. To test for to much food or lockout. Your next watering or feed. collect the LAST bit of runoff and compare it's PPM to what your feeding. If its dramatically different then you need to adjust your feed accordingly. If the PPM's are high( PPM + half the amount your feeding.example 800ppm comes out at 1200( 800+400) then you want to do a flush( no more feeding just water until runoff gets back into range) If the PPM's are even higher then that you might want to consider a HARD flush. Add PH water to saturate it and wait 30 min to let the salts break down a bit. Then continue to add water until your PPM's get back into range. ****Warning Hard flush is risky in soil. You can wash away all the good microbes in your soil and cause more harm then good. Soft flushes take longer but are a lot safer. Your using synthetic nutrients so its not as risky as an organic grow. Lastly if the PPM's are lower then you have a hungry girl and should increase your feed with that one. Also check your runoff PH and adjust your water accordingly. But never adjust out of range (6.0-7.0). Always keep the water going in within range and