its been my experience that each time Ive had a ph issues, that late in bud......... it did seriously affect my resin production, and there was very little smell to the plants, I grow mainly the same strains over & over so I know the diference

I have a meter like yours, I have a chemy Ph test kit, a $50 PH pen & a PH truncheon that cost $160.00 I can tell you those meters you have arent accurate, & cause you grief like your going thru now.
I wont even rely on my ph truncheon the chemy test is always needed as a backup test kit, when the plants are crying

look into a soil runoff test as posted above
Ganja Guerrilla Reviewed by Ganja Guerrilla on . Whaaa...? Day 59 of flower. Starting approx. 4-5 days ago, a couple of fan leaves (1/2 way up the plant) started to go a bit yellow with a bit of purplish/brown in the center of the leaves. It happened so quick I didn't notice whether or not it (the yellow) went from tips of leaves-back or backs-to-tips. Being a bit lazy, I just assumed it was a nitrogen def. since it has been in flowering with nearly no N for a couple of weeks now. (I just checked my soil pH too, right at 6.5-6.6) I think it was 3 Rating: 5