The University of Florida Extension Soil Testing Laboratory in Gainesville does offer soil pH and soil fertility tests, but usually pH or fertility problems would not be the main cause of rapidly dying grass. Diseases, insects and cultural problems like watering problems are more likely causes.

If possible, please lift a sample of the sod (about a 12 inch by 12 inch square) taken from the edge of an affected area and bring it to the Lawn and Garden Help Desk at our office where one of our horticulturists or Master Gardener volunteers will examine it. The sample should show a range of symptoms from healthy to noticeably damaged. It should be collected with about 2 or 3 inches of soil and roots attached. The regular hours for the Lawn and Garden Help Desk are from 8:00 am to 5:00 pm Monday through Friday.

A map and directions to the office can be found here: http://pinellas.ifas.ufl.edu/map.shtml