HELP! Are these FAST-SPREADING dark spots: DISEASE? PESTS? NUTES? WATERING ISSUE?

I don't have much time to post I just had to do this because it's an emergency! I will answer any questions you have regarding background information that may help diagnose the problem. So my girls are 3 Kushberry plants in week 6 of flower. I got them from someone else when they were in day 10 of flower and they weren't getting any love so I've been trying to save them this whole time basically. What I'm freaking out about is that the fan leaves have mostly turned yellow and died, which I was expecting at this point in harvest. I did have a very light case of spider mites, but I caught it and ended it early with no sign of return so far. However 2 days ago out of nowhere I opened the closet door and the leaves were yellowing from the tips inward with burnt looking, curled leaf tips. But the strangest thing is the tiny dark brown blotches all over the leaves. The blotches also start on the tips and work their way inward. I have had to cut off almost all of the fan leaves and its still spreading! PLEASE HELP me figure out what is happening and how to fix it! I will be so upset if I fuck up right as the trichomes are about 20% amber.

jeez man I dunno. It looks to be maybe lack of something in the nutrient department? Perhaps the mites are hard to see but existant and slowly feeding off those leaves. First I would use a magnifier and have a real close look. second I would flush my pots realllly good and third I would add I slight extra bit of nitrogen and micro nutes to your feeding sched. what's your ph at going in and your ph at runoff?

your so close just health them up and it's harvest time!! do you flush now and then?

Looks like a basic nitrogen deficiency to me, which is common, at this point. You could give them a tad more N than the've been getting, or you could simply finish them out. Next time around, keep the nitrogen levels a bit higher, a bit longer, and they'll stay greener, longer. Don't get carried away though, too much N can hurt yield, and make for leafier buds. It's a balancing act.