Dimples in top of hot water heater?

Electric hot water heater installed about 15 months ago, so relatively new. Happened to look at it today and noticed about 6ish dimples of various sizes showing in the top, and they are filled with a cream-colored substance. Photos attached.

I don't recall seeing these before (at the time of installation or since), but perhaps am misremembering. Today at first I thought they might be dust, but when I touched them they were completely solid. Nothing is wet. Nothing above the heater except ceiling, and everything around it looks normal.

What causes this and is it an issue? Should I call my plumber on Monday?