I have a Trumpet that was in my 20 gallon tank. At somepoint it must have fallen or got buried by my watchman goby. Months went by and then I found it buried. I looked at it and looked similar to what you are seeing on yours. I just set it back up and it recovered after a couple of weeks. As long as your tank is good overall water quality I think you will see it recover. Let us know how it does.