Yep, lisa is right imo, thats where i was going. I think you need a flust too. looks like nute burn. I bet the tips curled a bit and you didn't catch it. pound it with water
Are you alternating nutes and plain H20 to help flush the salt build up I have found especially in warmer grows that the nute then flush works very well especially with soil grows useing FOX FARM....... are you also useing the beastie bloom...... open sasame..... cha ching bloom enhancement products also?
MrCloner420