Burnt Toast

I have one chinchilla, Theodore, in a cage by himself for a few weeks. Yesterday, I bought a brother and sister and put each in their own cage. They came from another household and I have noticed that their poop was soft, short and round. I read that burnt toast can help. However, they didn't eat it from my hand so I crumbled it in with their food and hay hoping maybe they would get a little bit. I am not sure what the other family fed them so they are eating Carefresh Complete, Sunburst Gourmet Blend, Timothy Hay, and Timothy Hay bites broken up in their food dish. They have been getting fresh water. Is their anything else I can try if they do not get better in the next few days? They both seem fine. Running around and playing. They don't seem any more tired during the day than my Theodore.