can someone help identify?

I have 2 strains in the same system the problem is with the Applejack. Appalachia is ok. This is happening to most of the fan leaves 1 month into flower. Interior leaves and buds are ok.

A full plant picture would be much better.

deficient in micro nutrients. i'd try a very light (1/4) dose of some all purpose micro nutrient fertilizer it looks like maganese calcium and magnesium just my opinion it wouldnt hurt to give it a complete micro nutrient dose (by complete i mean containing all essential micro's) and only use a little here and there. But if you think its got enough of the micro's and youve been using cal mag id say it may be something different and u may just wanna let it do its thing if its only a few leaves

as Nizza says it could be mag or cal deficiency. if it's the older fan leaves and the upper ones are looking good i wouldn't worry about it. GL

Ok thanks guys. Ya I use botanicare calmag and never had any problems with other strains. I'll post full plant pics when the light shuts off.

make sure PH is on,

Ok so here are a few full plant pics:





What I don't understand is the Appalachia seems ok?!



I use Gh floragro 3 part and Botanicare calmag plus with RO. I've never had an issue except with this strain.

Bump for anyone with applejack experience

Nutrient burn. Advancing. Heed matt's advice on pH. It may be locked out already.

It generally stays at about 5.5 ph and doesn't move much. It starts off at about 1500 Tds when I do a rez change and drops down as time goes on. Is that too much?

Check this thread. It has helped a lot.
https://www.rollitup.org/marijuana-plant-problems/488004-guide-nutrient-deficiency-toxicity.html
This is just an opion but since you are in flower your girls require more maganese/magnesium and it looks like a tint of calcium def too.

Man this site has been great and i have a few more links to others that have helped me harvest a few crops over the last year if you want them.
Happy smoking

1500 sounds awfully high. What is your starting water PPM?

My starting water is usually at 100 ppm or so.