Looks predominantly like a potassium deficiency, but you should also check your water PH which for soil should be roughly between 6.0 and 6.8.
Slightly limp leaves could also be under/overwatering and you might want to check your water temps before adding. Your grow is quite warm (85 day/75 night) so if you add very cold water it can shock the roots a little , look for water temps of about 68 degrees.
Now you are in flower look to lower temps a little (78 day/68 night) in any event.
If you PM me I can send you a defeciency chart that covers most of the issues we face.