Hi Cheri, thanks for the question.

It is been shown that leaves mowed and left on the lawn can be beneficial by adding organic matter to the soil.  Of course, leaves left covering the grass can prevent grass from growing.  The more likely problem is the sandy soil. Sandy soil does not hold nutrients or water very well.  Some nutrients like nitrogen and potassium easily leach from the soil. Soil pH can also be a problem. A soil test will help to determine what may be missing.  Adding organic material, using time release fertilizers, and proper watering can help.  Sandy soils may need occasional overseeding. Now is a good time to get a soil test so you can be ready to go in spring. Check out the following links:

• https://homesoiltest.msu.edu/
• https://www.canr.msu.edu/uploads/resources/pdfs/mulch_fallen_leavesrs.pdf

I hope this is helpful.