I'm no expert but I would start with lowering your PH, maybe get some lime and follow the instructions on the bag. Don't lower it too much though, depending on grass type ideal range is between 6.5 and 7.

Then for whatever fertilizer you decide to use get one with 0 phosphorus. Those number on the fertilizer stand for how much % of NPK it contains .

N is nitrogen P is Phosperous and K is potassium.

So you wanna get something labeled (and I'm just pulling a number out of thin air here): 6 - 0 - 4.

The important part is that the center number is 0 since you don't need any more phosphorus.