Hi. If Pets At Home allowed three Chinese hamsters to all go together, that doesn`t surprise me because they are not the best at telling potential owners of what they are taking on. Chinese hamsters, especially females, should be kept alone because they almost always fall out. Males in a trio could prove volatile, but in the meantime, you must keep a close eye on the dynamics of these three for any small signs of bullying or any chasing.
Chinese hamsters are wonderful.
A big favourite of mine. But if you are new to Chinese hamsters, there are a few pointers for you.
1. Allow them plenty of time to settle in. They are naturally shy, but bold little creatures once they get to know you.
2. because you have three living together, it`s a good idea not to have any enclosed spaces where one might be trapped or bullied. Open ended tubes and an open nest with plenty of bedding is best.
3. No levels inside the cage as levels can cause them to argue over territories.
4. Have multiple water bottles and food dishes and also scatter feed.
5. Chinese hamsters are more like mice and love to `cling` and climb.
They can be prone to diabetes, so their diet can`t have added sugars or treats that contain honey, syrup, molasses or fruit. A good mix for them would be Burgess Supahamster Harvest ( the Syrian version) and you can add a bag of canary seed to this as they love small millet seeds. Canary seed contains hemp and linseed also. Dry mealworms are a good protein treat.
Hope this has helped a little. What cage are they housed in currently?
Edited to add: Oh and, if they are already adults, the scrotal bags that males have will be visibly obvious!