Ok, that sounds like maybe a do-it-yourself waterfarm type setup.

Yeah that PH is way way high for hydroponics. You need to be basically at 5.8 or as close as possible for these plants to take up the nutrients they need. If you have some distilled white vinegar in the fridge, then you can use it as PH Down until you buy some proper PH Down.

PH is about the most important factor, so keep it in check, else a slew of problems can develop all stemming from bad PH levels.

So really, there's no giving the plant a break or whatever. Keep the water level where it belongs with PH'd water for now and you should be ok.

I wouldnt worry over growth rate honestly, but focus on healthy water and healthy looking leaves and growth will naturally follow.