Howdy. Wondering on how to clean some "staining" on my Yankee Bay insert glass. I have been cleaning the stove all year using windex and paper towels. This last cleaning, I let the stove go for a few more bags than I usually do and there are some small silver dollar sized stains on the glass. They are brown in color. I'm afraid to try anything in fear of etching the glass. I have tried really scrubbing them with some glass cleaner to no avail. Any suggestions.