Raising your nutes should only burn it more. Why just one and not the others ? Keep an eye on it to see if it burns more. Being at the front by pump and in rockwool can cause it to hold too much water and nutes. more than the others.

Bend the top if you need to it won't hurt.

Your nutes shouldn't drop like that. I have never seen that much of a drop. Plants take in nutes and give off toxic waste. That's why you need to change rez every 10 to 14 days. Adding more nutes keeps the toxic waste. When your plant rez uses 20 litres of fresh PH water for topups it's time to change it.

Tell us about your water. R/O or distilled or well or tap.

I had a 6 plants that had worse tip burn from nutes and did about the best for me I had.

From the looks of it they will turn out fine. Mybe just one plant that's sensitive to the nutes.