Yellowing and drying leaves during veg

Hello everyone. Have to start off by saying everyone on this site has been great. It's my first time growing and I'm on day 33 of veg, have 30 plants. 8 are blueberry and 22 of a strain from my buddy's brother. Started using MG potting soil, which I've learned wasn't the best choice. The plants are in fairly small containers, so I'm pretty sure the MG nutes are used up. I've been on vacation for a week and when I came back i realized the plants were growing a little too fast for my friend to keep up with. Some of the top leaves got a little burned from the floros, but I'm not sure what the problem is in the pic below. I'm thinking maybe too much N, but thought I'd get info from you guys/girls. I've got a 600 watt HPS cool tube in the mail and intend on starting the 12/12 cycle this weekend. I've got some of plants under t-12s, and just started using a 400watt MH my friend let me borrow. Thanks again for all your help.

sorry, forgot to add the PH of the soil and water is OK, and I have a moisture meter, so I'm confident they've been getting the right amount of water

Those leaves do look weird. Like they were burnt or something. But they are not the top leaves, correct? Looks like they are towards the bottom.

yeah, they're towards the bottom. And they're like this on 2 plants on the leaves on both sides.

looks like nute burn. if your mg soil has slow release nutes thats probably why. or not a proper wet/dry cycle even with the meter. they are not always accurate esspecialy if you dont take readings in different ereas of the pots. i find checking the weight of the pots more accurate.