Weed Control and Dead Spots in Floratam St. Augustine

Floratam sod 2 years ago. Mow high, water twice weekly, never aerated/dethatched, bag clippings. Weeds in shade (veronica, groundsel, dichondra). Sprays say St. Augustine but not Floratam. Edge dieback and center spots. Used Sunniland for chinch bugs. The expert says Floratam has special label precautions; follow carefully for weed control. Mulching mower weekly, no visible clippings next day. Fence line dieback: check string trimmer height, soap flush for insects, catch sprinkler water to verify coverage. Fungus unlikely given weather but possible.