We don’t sell GrubEx so you might want to ask the folks where you bought it about how and when to use it. HERE’S a link to grub control using the products we do sell. The best approach IMO is to use Milky Spore grub control which you can read about through the link I provided above. Scott’s lawn food is just OK so I’d suggest you look into something better like our Country Estate Lawn Food line for lawn foods that are made in NY and we have ours blended to match the needs of lawns here in our area. Now through mid September would be a good time to add get some seed down to help thicken up the lawn. Often people ignore the pH of the soil and the grass suffers because of soil acidity…which is very easy to correct. HERE’S link to more on pH correction and late summer lawn seeding.