need advice on how to help my baby.

I have two plants in the ground and ive been fighting white flys and other leaf eating critters. these two plants are extremely unhealthy and only have leaves at the very top. they are started to flower though. all the bottom leaves keep falling off, yellowing and withering. I think heat and humidity isnt helping. i have some miracle grow fert, the blue stuff. should i water them with that? also is 7 dust ok to put on your plant? tell me what you think from the pictures. first time and i havent done much to the plants except water and 7dust once to keep the bugs off it.
the white stuff is 7 dust that ive been trying to wash off. also these came from a bag of bud not seed bank.
pleaseeee helpp. lol i want to salvage some bud from them if i can
sorry the pics are blurry
Thanks