Ok....*puts on shelock holmes cap* if both Mel and Jodi don't use detergent, or rarely, what about Nelle? If she doesn't, then maybe the wee is not being cleansed out of the nappy properly and so continues to eat and destroy the nappy in the background until one day it all just lets go with the force of the washing machine??

Just a theory....I hope you can figure it out cos it looks just awful. I just checked all mine and they are all looking fine! Phew!