Yellowing seedlings but not all of them(DWC)

So I have three second node sprouting seedlings planted in their forever homes of 3 inch net pots in an 18 gallon container trellised with wire for some extra support. I have 3 separate strains situated this way in a 48*48*80 under 600 watt MH. Nutes are Humboldt's secrets full line to try them. Running their A and B at system levels of about 45-55% for the seedlings giving me tds numbers running 467/495/655. The 655(agent orange) is one week further along. Corresponding pH level 6.1/6.2/6.0 last week. 65L/minute air pump to a manifold running to an air stone each

Problem is 2 individual plants, separate containers are yellowing a bit from the stems of new growth and I can't seem to figure out what the issue is. Pictures included to help. Any sound advice would be wonderful

Lots of nutes for a baby

Try 10-20% strength
Be sure u have an enzyme cleaner like hydroguard or z7

I can do that no problem as today's res change day so problem is probably nute burn?

Yer trying to burn em up

How high is the water below the net pot?

Sounds good. But why would only 1 of 3 per reservoir burn?

BobThe420Builder said:

How high is the water below the net pot?

Click to expand...

Water is touching base of Rockwood cube

Drop water to 1" below the bottom of the net pot
Could be drowning them, rockwool is notorious for that

Every strain is different, just like kids, some like broccoli, some don't

If it's below I assume that encourages outward growth versus making it too easy. Makes sense. I'll go fix levels and stuff now thanks man