Yellow tips show up after switching lights to 12/12

Hi folks. I’m looking for some thoughts on what might be happening here. I’m growing in a 4x8 tent, lights on temp around 77 - 79F. Humidity between 40 - 50 RH. Im growing in fabric pots with a coco perlite mix. Remo Nutrients (full lineup). My PH going in is between 5.8 and 6.2. I do test runoff PH which is usually right around 6.5, although I’m not sure how valuable measuring PH runoff is....

I have been running about 700ppm in veg and have seen very healthy and rapid growth.

After I switch lights to 12/12, after 3 or 4 days I start to see tips yellowing slightly. It starts at the very top and slowly the leaf tips yellow moving down the plant, but again it’s showing in the new growth.

The problem never progresses beyond the tips and I’m able to finish a flower cycle with nice results.

My thought was nutrient burn but I have been running flower nutrients at 400 - 450 ppm and it just doesn’t seem like Nute Burn to me...
I water / feed daily with plenty of runoff and my runoff PPM is never higher than 100 PPM from what is going in.

I have attached a few pics for reference.

Anyone else see this type of tip yellowing after switching into flower?

Any suggestions on how i can adjust my Feeding / environment to prevent tips from yellowing out like this?

Thanks!