First indoor grow- problems in flowering

[4tyres]

Hey forum,
Been slow in flowering stage but looking good till just recently ‘ see pics
WTF?... don’t know type, friend donated seeds. Using cheap LED with different colored lights ,no heat, any help would be greatly appreciated!

Just the top leaves nearest lights-light burn?

 

[AgentPothead]

Looks like late stage calcium deficiency to me bro. Are you supplementing magnesium already cause too much can cause calcium lock out. If you are not, I might hit them with some CaliMag. PH can cause lockout issues too, do ya know your PH?