Any clue what this could be?

I am using a DWC. This is DJ Short Blueberry. This is 4 weeks into flower. I am using GH flora series. PPM is 700ish, water temps are 68 farenheit and PH is 6.0. Using a Black Star LED. The plants did suffer from root stunting in the first few weeks from seed due to not having a thermostat on my water chiller resulting in 50 degree temps.

Are they still suffering from lack of roots? Are my nutes too low? I was thinking maybe it was due to the LEDS being too close but I ruled it out since not all of the canopy of my SOG is affected.

i just raised my ppm to 1000. My previous grows I would be at around 1200ppm by now but I was told Blueberry didn't need much nutes.

You need a brighter picture

From those lousy pics it looks like nute burn. But one cannot really tell with pics like that.

Is this good enough? My LEDS were messing with the leaf colors so I broke off a real bad leaf off a smaller popcorn bud. I also notice I have alot of purple and violet stems. Is this normal for Blueberry? I remember growing g13 Lab Purple Haze that did that as well. Also I don't think a plant can suffer nute burn at the 4th week of flowering at 700ppm.