Not sure what's the problem?

Came back from a long weekend to see the picture below. Ph had spiked to 7.5, not sure how long the plants were in it. Was 6.0 3 days prior. Thinking some ph burn? I normally run 350ppm on young plants, diluted it for recovery. Any help would be appreciated.

Rubbermaid dwc
Blue Plantet Bluemax 2 part nutes
pH 6.0
PPM 150
2 weeks into veg
600w HPS 24/0 cycle 18" above plants
Daytime temps are 70's f, nighttime 50's f

Obvious nitrogen deficiency. You need to feed it more. 7.5 wouldn't cause any problems whatsoever, it's just not ideal.

Yes, I would say nitrogen deficiency as well.

50F night time temp is a little cold. Plant growth will slow at that point. Your plant will lose vigor.

350PPM is too low even for a smaller plant. I run my DWC buckets at around 600PPM for young plants in veg and up it to around 1400PPM for full size flowering plants. And Medicanman is on point with the info about your temps being too cold. You may want to try to run your lights during the night when it is cold to keep the temps in a decent range. I have the exact opposite problem where I live. It is always hot as hell here and I have to worry about keeping my temps down.

Thanks guys. Bumped up nutes and closed room door to bring nighttime temps up. It's normally hot here so I usually leave the door open. Plants have perked up. Thanks again.