Problem getting worse... Can anyone help me with this, please?

Novice grower (only second time growing and first time from seed) leaf issues.
Started 12/12 almost two weeks ago. Had to move the plants into another room as they got much larger than what I had expected. They are long and lanky but the bottom leaves is where this is happening. They are in the growing phase and I've got serious calyx coming on right now, I can't loose them now!!

PH: 6.5 going in and coming out
Lights: LED Cree COB 300w, about 18" above the top leaves. (The leaves that this is happening to are at the bottom and the middle of the plant. The top growth is great)
Nutes: Used Beasty Bloomz with the feeding before I started 12/12 - then was advised that it was a Cal/Mag deficiency with my last plea for help, so I ordered some Cal/Mag and administered that over a week ago. I fed again today, with Nukehead's bloom formula, it is a 10-52-10. Prior, in Veg, I used their 20-20-20 but only at half strength. It kind of burned them once with regular strength so adjusted accordingly and they have done great up until two weeks ago.
Medium: Soil
The temp is constant between 75-77 degrees and humidity is around 50%.

I sprayed with Neem prior to flowering (with NO lights on them) and soaked them really well to address some gnats. Have attached a couple of pics. You can see how the spots start out and eventually the leaf turns a limey green and then turns brown and dies.

Any assistance is much appreciated.

Thanks,
TAMJ