pH Lockout Help

I think I have diagnosed my plants problem as pH lockout, but I am not 100% sure. My pH fluctuates between 5.6 and 6.8. I check it about 3 times a day. I have a small DWC setup, with about 2.5 gallons of reservoir water. I was wondering about some techniques to combat and prevent this. I am using Fox Farm Grow Big at 1/2 strength. I am also due for a reservoir change in 3 days, so I might up to 3/4 strength. New growth on top of the plant looks excellent.

So, for all you hydro growers out there--

How do you all combat pH lockout/burn, besides the obvious answer of controlling your pH!! Here are some pics...


Both plants

pH lockout on bigger plant.....

new growth on bigger plant.....

Thanks for looking! I'm hoping to throw these babies into flowering in a week or so! Any help is appreciated!

flush now...use clearex and water for 30 mins...or straight water for overnight

Thanks toke! I know this is gonna sound like a dumb question, but sorry, I'm baked right now. I am gonna flush with straight water overnight. Should I pH my water to 5.8? And then i would just add my nutrients tomorrow? Thanks!

bump!!!!!!!!