Are the bulbs seated into the twist locks correctly?

If not, curious if the bulbs themselves are leaning or favoring a side, causing the heat to travel, distorting the housing, and peeling the Crome off the housing interior.

That's all I can think of that could be the issue.

What does the plug that connects to the bulb itself look like?

If one of the port holes is burnt or melted, this would also be the culprit causing the additional heat.