Leaves turning brown and yellow at the beginning of flowering?

I started flowering 3 days ago. I slowly began to notice the leaves turning slightly yellow along the edges and then brown spots began to appear. This is only happening to the leaves at the very top. What could be wrong?

Maybe heat. those new leaves are very delicate. also could be over nutes. i had the same thing happen. the large mature part of the plant handled the nutes but not the tips. it actually burned it enough that it ended up topping my plant. Check the temp right at the tips because if its fine than no harm done. Then if you can't check the soil flush it. an underfertilized plant is better than an overdone plant. good luck