I have used humidifiers for many years-Dampits(green tube), a greenish-brown stain appeared on edge of sound hole of Gibson my j250 about a week ago. Looks like it came from tin closer on end. It also looks like it could be mold or something else organic . I am very concerned it might spread-about the size of pencil eraser right now. Looks bad but I am more concerned about structural integrity being compromised. Best guitar I have ever played or owned. This has never happened on any other instruments. I really need advice and any info anyone has. I have been on this forum for many years and have never read anything like this!!!! HELP!!!!!!!!!!!!!!!!! Scott