I'm going to try not to sound too technical: Shit happens.
Those tips are probably from the issues you were having at the beginning of your grow. I have never had a grow without at least some tips being browned. The rest of the leaves look fine.
Something for the future. What you have is old damage and there is nothing to be done. The tips are brown and dry. If they were light green, yellow, or some other necrotic looking color, it would be new damage you can have a bona fide worry storm about.