I think granulated sulfur should work. But ironically I’ve never had the problem yet. Have you tried googling it?It tested PH of 7 even, i know i have to lower it so i added the chicken poo an mixed it around im gonna get them as bushes, just other than chicken poo i wasnt sure what else i could add to lower it an have it not be to acidic by the time i plant them im hoping to have them in may June if i can get the soil right