Nitrogen def, or something else?

So, first time grower here. 3 Blue Mystics in 70% spaghum moss / 30% Perlite, 1st day of week 4. Im aware there lacking height for their age, I've topped them for 4 I mains, and done a little lst, and I think the def has resulted in a little stunting. Ive lost 1 set of leaves so far and the pics are of the second set thats almost all yellow. Is this a nitrogen def or something else? The necrosis spots in the second pic were from something else a week or so ago. It is a yellowing that works its way back from the tips, but as you can see, the veins stay green until the leaf is about to fall off. I fed them yesterday and it got a little worse today. last feed was at 6.7ish, about 80 ppms of botanicare pro grow. I'd raise the ppms but im getting a little tip browning on a couple leaves, which makes me think that this is currently all they can handle. Thanks for the help guys.

I'd say nitrogen deficiency. 80 ppm seems low to me for week 4 but I'm not sure because I use tap water. I think the browning could be from the plant "feeding" off itself, but I'm no expert.

+rep for the fast answer

Yeah, I use tap water too, its about 150 naturally, and tested about 230 after nutes were added. Is that more like your numbers? I normally water every two days, but do you think I should step up the nutes a tad and feed again tonight? Theyre still maintaining vertical growth since ive moved the lights farther away, about .5 inch a day, but id rather not lose another set of leaves.

I'd say step up the nutes. Do you feed every time you water?

Nope, just the last 2 or 3 times, trying to fight this off. It's been straight water pretty much from seed. I expect after I remedy this its gonna be a feeding every other water.

Then they definitely need nutes.

Cool, just spooned in an extra half table spoon of pro grow and a quarter tablespoon of liquid karma to the normal 230ppm solution and watered with that. If that doesnt help them I'll keep incrementing the amount up. It should at least prolong the life of my troubled yellow fan leaves hahaha. Thanks again man, I'll update with some more pics tommorow.

I recently experienced stunted growth. I cut down on dosage of Pure Blend Grow/Bloom nutes and growth is normal now.

https://www.rollitup.org/marijuana-plant-problems/488004-guide-chem-deficiencies-abundancies.html#post6648220

Look for your symptoms here, this thread is fantastic.