Green poison, Cal or Mang def.?

Sweet Seeds Green Poison..
3rd week of flowering.
Botanicare nutes (light feedings with plain water intervals).
Temps never go over 85.

Pics arent great, but the synopsis is: A handful of the mid-level fan leaves are showing yellowing from the tips moving to the petioles. There are brown spots that progress along with the yellowing.

Its so hard to really judge the exact deficiency..

Opinions?

Could be Potassium too..

I'm thinking potassium or ph lockout

I wish I still had my digital ph meter.. been using the ol dye drops.

I doubt its lockout though.. none of my other girls are showing any ill signs.