Bern the other thing I could think of was that perhaps the bamboo isn't 100% dry and still a bit damp if the weather is so bad. If you're putting them in the drier tho im stumped.
I had one CT go mouldy and I used canisten rinse and I haven't had any issues with any others. You can get canestin from woolies in the laundry isle (they hide it along the bottom shelf here )