Leaves turning more yellow - why?

Hello my friend, this plant is hungry because you give the wrong ratio nutrients. Give every liter 0.5ml grow, 2ml Bloom and 1ml Top Max. You can also just check the nutrient feeding scedule on the Biobizz website or even on google images.

0.4ec, not feeding enough. Try mixing up your nutrients then diluting down to your desired EC. and if it is to low to start off with, double the amount and work back from there. Confirm your PH does not go below 6.2, Biobuzz says it does not do well in lower PH. Good Luck!

Your plants look like they need more feed in my opinion. Definitely more bloom nutrients. Increase your feed and the color will come back.

the epsom should just be included in fertilization. Foliar sprays are a great reaction to a problem for immediate local relief of a deficiency, but a terrible way to feed on a regular basis. I see the initial signs of interveinal chlorosis and some burnt wavy tips here and there. if not giving 50ppm mg or equivalent in any slow release thing going on, it could be mg-related. Mg symptoms present 5 weeks after the deficiency exists. if chlorosis is centralized along margins and serated tips of leaf blades which lead to burned margins/serated tips, then it could be potassium-deficiency. Seems more interveinal to me, but pictures are deceiving. the burnt tips (end of leaves) can be several things. i'd wait a second. If you see burnt serated tips around outside of leaves, boost K a bit. If it remains interveinal and you suspected Mg before, boost mg.. in the fertilizer. nutes go in through the roots. that's what they are made for.

Hungry for potassium. Reduce the grow and increase the bloom.

Your tall one is a touch pale, which makes sense since it's been stretching more. If you're done stretching I wouldn't chase it though unless it gets worse.