Yea bro they looking good. No worries, the leaves turning yellow is just part of the flowering process. Also there is no more need for feeding your plants or adding anything. Just use plain water to flush for the next two weeks or so. They should get perty nice within that time frame.
Somewhere I had heard or read that for the last week or so, before you harvest that you didn't really even need light b/c then they would put their focus and energy on riping up that bud. BUT you may want to do some research on that before thinking about trying that.
And as far as picking them for harvest, I WOULD wait till the hairs turn red AND start curling back Into the bud. To me that's when the bud looks the best and ready to be picked and smoked UP!