I have yellowing of leaves in one of my WW auto seedlings. The other five look fine. It’s exactly 1 week from breaking ground for the one in question.
Soil: Coco Loco
Water: DI w/ cal-mag once since sprouting
Light: Spider Farmer SF-4000 at 30% and 30" above leaf tip.
Environment: Tent @ 75 F 65% RH
Any advice?
Are you phing water as this can cause this but I’m just a beginner bro
I did not PH the water. I didn’t think you could with distilled.
No I don’t think you can I used distilled on first grow and messed my palnt right up got a pH pen and started a new one she’s five weeks in to flower the now
Looks like it may have hit a hot spot in the medium. But I would definitely get a good PH pen. Apera makes a good one for about $50 on Amazon.
That’s not veragation. Those leaves are burnt. Veragation will cause yellowing all thru the leaves. As they are are small and young, I wouldn’t worry. Unless it continues thru the next nodes. 
That’s what I thought as well.
No nutes yet, other than a bit of cal-mag. The medium is pre-nuted, good for 3 or 4 weeks. I’ve got PH and TDS pens. I think I’ll flush well with DI and measure the runoff. If it’s a hot spot that may flush it out.
Distilled water is neutral at 7.0. I use tap water and distilled for slurry testing. Regardless your PH for coco should be 5.8-6.0. I want to say it looks like an iron deficiency but that would be very rare for now. Since you have distilled water which contains no trace minerals for later feeding. I would use the distilled water and take a medium sample near the root zone and run a slurry test. Careful with this since their so young. But that will tell you your medium PH 
