!! HELP !! I used to much PH up and now my plants are dying !!

So I have an Ebb and Flow system. My digital pen went out of whack before feeding causing me to put to much ph down (Advanced Nutrients PH Down Concentrate). I went out and bought another pen and put ph up to counter balance the ph. Now, even though my ph is 5.6 after putting alot of ph up (General Hydroponics PH up), my plants are dying!

What do I do?

I planned on draining the reservoir's, flooding the trays with plain water, draining them again and then putting nutrients.

Just drain and refill your reservoir with properly PHed nutes.