heat stress?

OK i have two lovely ladies right now, the one on the right is 6.5 weeks into flowering the one on the left is about 4.5 weeks into flowering. The temps in my room usually sit between 77-82 degrees while the light is on. The tips of the leaves are yellowing slightly on both. On the one on the right two of the fan leaves about half way up the cola have some discoloration going on. I have only fertilized that one twice, once a quarter strength, and a week later at half strength. Some of the leaves at the bottom of yellowing but i believe that is normal at this stage. Any ideas whats going on?

N def. but since you just changed to Flower nutes, plant is adjusting to them look looks norml. ;P good luck and keep on smokin'