You can cure it with tissue culture. Its important not to let your plants touch and you gotta sterilize your pruners with bleach, alcohol doesn't work.
it's most likely a deficiency if you flushed all the nutes out of the coco. just hit them with some nutrients and remove the leaves with necrosis on them.
Thats an odd looking strain. Looks very sativa to me. I don't think its your growing technique. For week 7 those nugs look extremely under developed but if its a haze or something with a long flowering time then I think ur still good.