I suspect a problem developing from mulching too many oak leaves. It looks like the grass is thinning in the area where I have been mulching them for the past 3 years in the fall. I don't notice this where I mulch gum leaves, pine straw, maple leaves or hackberry. I know that grass has a hard time living under and around oak trees anyway, but this looks like it is getting worse as time goes by. Hoping that some of you soil analytical types could suggest the right mixture of fertilizer for this condition. I probably need to get some fert going before spring gets here, right? I would sure hate to have to quit mulching, but am open for some help.