Not an emergency , but help is needed

Me and my bro have 6 plants 2 Blue Dream , 2 Sour Diesel 2 Super Skunk . The Super Skunk is getting brown edges , and on the tips . But the other 2 strains are fine . Is this Nute burn ? Or just water burn ? Although we watered just when the lights went off . So they had 6 hrs to dry before the light hit them again . tia
Using sensi-grow 600 ppm

dif strains can handle dif amounts of nutes. coz u got a few dif strains there, they will all react differantly

so could be slight nute burn. nothing major. dunno what water burn is mate. unless u talking over/under watering

lol ya imma noob . I was thinking if there were water drops on the leaves and the light hits it , that it would burn the leaf . Thats what I was calling water burn . Thanx for the input . I think those 2 plants still look kick ass but just not as good as the other 2 strains .