yellow top leafs

Hi , does anyone know what it can be? its first week flowering nothern lights, i struggled with nitrogen deficiency recently and after 2 weeks of healthy grow
they showed yellowing tips- just at the top of the plant :/ could it be too much nuts? i feed them with biogrow 5ml per liter once a week

how close is the light?

30-40 cm i would say, temp in the box-27C

Kind of looks like minor nute burn. If it doesn't get any worse i'd ride it out. You may want to give less nutes and work your way up. What size pot? You may need to transplant soon.

yep im afraid its burnt ... pots are really big

usa inches and fahrenheit plz