Simple solution.
Take 2 cups of water, 1 cup of beer, 1 cup of amonia, and 1/2 cup of epsom salt. Mix this together in a spray bottle of some sort and go out and spray your lawn.
The water won’t do much but equal out the mixture, the amount of water applied really doesn’t help anything.
The beer will feed the root systems.
The amonia will kill and diseases that are living on the grass.
The epsom salt will work as an aerator and help the water penatrate the soil.
Spray this on your lawn and in a couple of weeks your should notice an improvement!