A couple of questions for you:
Are you checking your PH?
It is looking like a nute burn when you were flushing with your R/O water did you let a good amount of it run out the bottom of the pot?
How hot is your grow space?
If the PH and temp are ok the plants should recover after being flushed, I usually don't have mine get so bad when I screw up but I only run half strength nutes on them.