I'm guessing that you used 3-way Ester. 1oz per 3 gallons of water, per 1,000 sq ft. I always spray 2 gal per 1,000. My app should be more likely to burn, than yours. Even with warm temperatures, I believe you can apply this below 80 or 85 degrees. Drought stress will also cause weed controls to burn desirable turf grass. The only time in 20 years that I burned any fescue, I didn't recirculate the product in the hose after letting it sit overnight. I didn't worry about leaving fert/pre/post overnight in the hose for quite a while, before I burned some turf (600 sq ft). It usually wasn't a problem.