I think it could be a virus, but then some fungal infections look like this.... There's no way to know unless you send a sample to a lab, and have it tested. If u were in the US, I would recommend Critter Creek, but since you're in Taiwan, I have no idea... Sorry. Good Luck tho! I hope it's not virused! But, just in case it is, I would separate it from the rest of your collection.