Lots of things all at once

Okay, first grow, first post. 10 plants in a shed split up into 4x6 veg room, 8x8 flower, and small storage/controls room. Veg In soil fox farm ocean forest 1:1 with promix. Veg lights 500 watts worth of big Cfl's and fluorescents, and 400w HPS only used during last six weeks before flower, started off 21/3 and worked down to 18/6. Plants 4.5 months from seed (unnamed strain to my knowledge, sativa Dom if not pure, friend of family has not tampered with, been growing same strain since the 60's) showed slow growth N toxicity throughout veg thought it was just slight overwatering until I used nutes (technaflora recipe for success) week 10 thinking what was in fox farm was used up but N tox got much worse. Transplanted from 3 gal to 7 gal using straight promix to avoid adding more N with fresh fox farm straight filtered ro water ph 6.0 for 2 weeks. At same time bugs outside were getting bad and very hot so i closed the room off to fresh air and added 5 exhale c02 bags. Temps always well maintained, started looking better, growth rate increased moved to flower added flower nutes (flower lights 2-1000w hps in well vented hoods). 2 weeks in flower only added the nutes once still showing N tox, found a few spider mites, decided to flush to remove N and spray with 1:1 rubbing alcohol and water to kill bugs. Flushed day one with 7 gal each filtered RO ph'd 6.0 day two 10-12 gal well water, tested in past not real bad don't remember exact results, ph 6.0 to 6.5, runoff started ph 7 got down to 6.5. Alcohol spray same day as flush looks fine day two far fewer mites (only found one) sprayed again after flush day two. Day three I come into major damage not sure if it's a nutrient deficiency looks closest to mg (flushed all the nutes out and need to add flower nutes?), nutrient burn (didn't flush well enough pushed all the nutes on roots?), or alcohol spray burnt leaves (which I doubt, didn't happen first day moved lights 2' further away on day 2). Pic two is of worst remaining N tox and mite damage, hard to make out color in the room so I moved one outside for a sec. Any help will be greatly appreciated.

so you got lock out /burn and mites?

i mean you are doing what i'd do flush and restart the nute process.. but when you renute maybe use half the dosage? also treat the soil with water with dunks in it.

Mg deficiency was best I came up with. Did a light Epsom spray would really like to let it dry out a bit before watering again will see how it looks tomorrow any worse will do a half nute water fabric pots so will dry out quick.

you should be doing a HEAVY(1 teaspoon per liter of water) epsom foliar spray. Doing it at a light ratio is wasting time and epsom salt.