Light burn or something else?

Possible calcium deficiency. If you are already feeding some calmag then it could be a lockout issue . So you need to check your PH going in and going out . Check your run off PH, and if it's massively off you should feed extra volume of water(or your nute mix) at the correct PH until the run off is at an acceptable PH level . It doesn't have to be the same as what you put in . But you don't want it miles off as that can cause lockout issues. Hope this helps . She's coming along nicely 👍