This could also be air circulation. Most ripening fruits give off ethylene gas, which has the effect of speeding ripening in a feedback loop. That's where the e

This could also be air circulation. Most ripening fruits give off ethylene gas, which has the effect of speeding ripening in a feedback loop. That's where the expression "a bad apple spoils the barrel" comes from. But the extra bacteria is indeed more probable, especially if you notice that the kind of mold growing on the in-house fruit appears to be different than the ones left outside.