Recommend you take some samples of the stool and send it to the vet.
This is also one of the reasons not to get lots of other pets in addition to chinchillas... chins are semi-fragile creatures, and if money is tight, it's probably a good idea to budget in a cash reserve for bringing them to the vet, rather than spending the money on enlarging your menagerie.
There's no point having 5 different pets and you can't afford the time or money to take care of them, much better keep it at 2 pets but you take very good care of them.