Answer: Dead spots in the lawn can be the result of droughty conditions, but they could also be from compacted soil, grubs, fungal disease or even dog urine. In all these cases, digging the soil to aerate it will help. It will raise insects to the surface so birds and weather can destroy them, loosen compacted soil, expose pathogens to the fresh air and help the salts from dog urine be leached away. Since you've tried most everything I think the best course of action is for you to rake out the plant debris in the affected spots and dig the soil to loosen it then rake it smooth and over-seed with fresh grass seed. The seed should germinate in 7-10 days and fill in the spots. Lawns require lots of water so double check to make sure the spots in question are getting enough water from your sprinklers.
Best wishes with your lawn!
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