Dave, I would not feed all the other hives, if there is a flow going on they need to harvest nature. You will need to protect this young colony until they are developed enough to have enough guard and forager bees themselves. This could be around 6 weeks for a fully developed hive. Good that you caught what was going on, they really need your help right now and it looks like you are doing just fine, yeah!!! There is nothing wrong with protecting a colony. The bees would really like to have sugar syrup so close to their home, instead of having to go out searching for nectar, that is why this robbing began. Good luck, you're doing just great!!! Beautiful day in the wonderful life we are all livin' and sharin'. Cindi