rusty leaves

Hi, everyone, I have a question about my plant. This is Granddaddy purple auto flower plant. Its 70 days old. It is planted in fox farm ocean forest potting soil. with 25% perlite. I feed it fox farm big grow at 1/2 tsp per gallon , FF Tiger bloom @ 3/4 tsp per gal. and 1 tsp Big bloom per...