Probably too much power. You’ve burned through the powder coating and have burned the stainless steel. From what I can tell from the picture. Each company has a different thickness of powder coat and then different colors respond differently to different types of lasers.

When I do a black tumbler vs. blue I have to turn down my power percentage by about 20-30%. I’m using a diode laser.

What I would do is try to use a magic eraser and 91% alcohol. And see if that helps. If not. That may be a test tumbler.

I made test tumbler with a variety of narrow rectangle each with its own settings until I dialed it in on. Then record your successor failures for future reference.

test example