What's this deficiency'? Plants are around a month old

[Jaydubbz2108]

I have about nine seedlings that are around a month or so old three of the plants are showing this yellowing around the edges of some leaves and it's only in some plants not all of them... Growing in Roots organic 707 transplanted from Solo cup on 84 into 1 gallon fabric pots using Roots organic 707 have only watered with recharge and it's in tiny bit of Cal mag.. under blurple LED at low power until flower tent is done in a few weeks

 

[Jaydubbz2108]

I have another plant that's a little older maybe a month and a half that started showing these signs first and it progressed a little harder I'll show a picture next

 

[Jaydubbz2108]

The next photo I show you is a plant that's just a little older maybe a month and a half old started showing these signs first still haven't really corrected the problem either cuz I don't know what to correct

 

[Jaydubbz2108]

Plan is just generally pissed off all the way around, I don't know yet but I think my pH pen might be broken the only thing that makes it to where I'm not really looking at that is I know in my five gallon bucket all I have to do is use a capful and it gets it in the right range I just used the pH pen to tweak it a little bit after that but I'm wondering if that is the problem would it look like this? Any help and input would be appreciated!!!!!

 

[Jaydubbz2108]

Also a couple weeks ago I found a couple thrips on a couple plants but not anything too crazy but I did get some insecticidal soap and sprayed them with that pretty thoroughly and waited hours before turning the light back on, I also have used neem oil, and also tweetmint.