Leromeanswered grow question 3 hours ago Hey growmie,
this looks like a magnesium deficiency. Calcium and Magnesium are needed in bigger amounts when growing with LEDs most of the time, especially in late veg and early flower (during the stretch)
I suggest a CalMag supplement for this grow.
For your next grow you could prepare the soil with amendments like raw gypsum (calcium sulphate), ultra fine basalt or granite rock dust (besides calcium and magnesium it will provide many micro nutes like iron, copper, zinc, silica,... aswell), , epsom salts (magnesium sulfate) and garden lime (calcium carbonate) . Its good to have those 4 + a CalMag supplement on hand anyways for every grower in my opinion, especially when growing with LED´s which for some reason force a higher demand in plants for calcium and magnesium.
Good luck and happy growing!