I'd guess condensation too. My workplace is inside a corrugated metal building and condensation dripping inside is definitely a thing depending on humidity and temperature differences inside/outside the structure.
If you're concerned, add more dry bedding to help dry it out more, or swap it out. I think it's fine as-is though.
If you're concerned, add more dry bedding to help dry it out more, or swap it out. I think it's fine as-is though.