I am not trying to bust your balls but for gosh sakes, have some patience. Flushing is a good start but it is not going to be the cure all of your problem. I have no idea what your Ph is and that can lead to lock out as well.
What nutes are you using? IF, it is in fact a P or K def, then I would suggest a supliment for your normal feeding schedule. PK 13/14 is a good one and I have just recently started using Hammerhead (PK 9/19) Again, not knowing your nutes or their NPK ratio, it's hard to determine.
Regardless of what your issue is, don't start changing 3 or 4 diffent things because you will never know what "fixed" your problem. Have patience and just use common sense. It will take 5-10 days once the proper action has been implimented before you see improvement. The damaged areas will not heal so remove any damaged areas that are more than 50-60% damaged.
Again, relax and be patient. Oh, one more thing, your temps could also be a factor in how your plant uses it's nutrients. Monitor that as well and keep it between 60-80 degrees farenhiet. Good luck