Answer: When sod is first grown it is on an especially mixed medium that encourages strong and healthy root development so I don't think the original soil in the sod is causing a problem but I do wonder how your landscape was prepared prior to the installation of the sod. If it wasn't worked and raked and then rolled, just as you would prepare it for seeding, it is possible that the roots of the sod are having trouble penetrating the soil in your yard. If the soil was compacted or hard the roots may be simply sitting on top of the ground rather than rooting down into the soil. See if you can pull up the sod by inserting a screwdriver into it and pulling up. Do this at a corner or where the sod meets a sidewalk or driveway. If you can pull it up in sheets, it hasn't properly rooted. In this case you may need to rent an aerator and run over the entire lawn. An aerator will remove plugs from the sod and also from the earth beneath the sod. This will allow the roots of your St. Augustine to penetrate into the native soil. It might be a lot of work but I think it will save your lawn.
Best wishes with your project!
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