No spider mites that i can see, so your good there. If you haven't used any nutrients, i would baffled of why your plants are showing nute burn now instead of when they were younger plants. Fox farms soil tends to be hot and burn younger plants, not wait until mid flower and then burn them.

Looks like cal/mag defiency to me. Distilled water has NOTHING in it in terms of trace elements and eventually your plant will use up all micro and macro nutrients in the soil. I think its time that she gets a dosage of some Bloom Nutrients.