Rusty Brown Spots

Its very likelly to be a calcium deficiency and possibly a magnesium deficiency aswell, now this could be caused by actually lack of those micronutrients, or it could be caused by an excess of phosphorous or potassium or both even. it could also be from overwatering. from a bad ph in the water. Now its up to you to know what have you given the plant later on, did u give her Bloom nutes? if so it might have been a too strong dose locking out calcium, magnesium, iron and zinc, considering that your other grow questions features pictures of a zinc deficiency then i would guess you gave a too big feeding overall across the tent but some plants didnt react well and locked out on nutes. I would give it plain water for 2 waterings and lower the nutrient dosage then keep them alternated as 1 h2o irrigation, then the next watering using a nutrient solution, then again just water, etc etc. actually im having the same issue :) And i'm fixing it, already gave it an extra dose of pk to confirm its a reaction to the phosphorous and potassium excess and it actually is indeed so now its just plain water for a bit and everything is fine. Stay lit growmie.