What are the temps of your roots? Do the bags or pots feel cold to the touch? The times I've had problems with my plants and flushes or adding nutrients didn't help it was because I had my grow bags and pots on a cement floor and the roots got too cold to do their job. 70 degrees F is around where my grow bags are at now. I have a way to check my Ph, so I know that nutes weren't getting locked out because of that. Took a little thinking on my end to figure out.