White Substance on St. Augustine

I noticed this (see links below) on My 7 Week old St. Aug Sod this morning. The new sod has been doing great so far. It has rained a lot the last week here. Sod get sun filtered through trees. I had put down cornmeal 2 weeks ago to help prevent fungus.
Anyone know what this is? It feels like a marshmellow and comes right off if I pull on it. Some of the leaves are turning yellow and have spots.
If this is a fungus what should I do? Thanks for your help.
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