well your problem is more than likely the mg soil, it`s no good.
the hairs have nothing to do with any of this. the hairs can go orange in the first part of flowering from heat. your to far in to flowering to start nutes, you wont have time for a flush.
the mg stuff salts up to easy, probably from wrong wet/dry watering.
with no leaves left your fucked, sorry. i would just start my final flush for harvest soon.