Separate the weeding and the feeding for better results.
I have a bit of everything. Tons of clover and a good bit of crabgrass.
Try MSM Turf (metsulfuron methyl ) can spray on st augustine safely for many broadleaf weeds ! Safer than 2,4-d and Tri-mec! Make sure to use surfactant, not Joy soap!Try atrazine. Don't wait until it gets really hot though.