Are you running any cal/mag? 1100ppm seems high to me if you are talking about x0.5 ec.
I run mine around 700 total with 100ppm cal/mag and about 15ml protekt. The protekt acts as ph up and has a lot of ph buffer... if you use it you have to put it in your water first before anything else. Cal/mag deficiency (not sure which) was causing my ph to drop, and then I got more deficiencies from ph lockout. You might not be getting enough cal/mag with the lucas formula, my ph drop was hardest when I was using sample bottles I had of GH Flora 3 part.
I would back off to 700ppm (x0.5 conversion) and run a little cal/mag. The protekt is good, but probably won't fix your problem by itself. And of course everything else... root zone temps, bubbles, light proof, bennies/sterlizer, ambient temps, air flow, etc. Any of that shit is not good enough for the plants and they will let you know.