The color of the leaves

are you pouring your nutrient solution all over the leaves? serious question

when plants have a heavy light schedule they need more Mg and calcium , always grow with cal mag, there's a big difference

Cal/Mag fix problem and trim

I’m going to have to agree with Growinggrannie it may be another type of deficiency but it looks just like what I get on my blue dream strain after about a months of veg it’s the only strain that does it, if left unchecked it gets real bad and takes along time to come back (the leaves will never go back to green but if you fix it they will stop turning) and If you just cut it off without fixing the problem firstyou will notice that it speeds up the problem substantially, I recommend advanced nutrients cal mag because it has a lot of other things that could be deficient, I noticed I can mitigate the problem all together by adding cal mag (I use GH because I’m cheap) to my cloner and feeding the large plants once a month

That looks like a bad case of calcium deficiency... but you don't have a diary going so it's really hard to tell. Get a diary going and join the community! It will help all of us to help you when you have questions or run into trouble... Good luck