I feed the entire tank the same variety of frozen. On days I fed Betta pellets I fed aquatic frog pellets. Put the frozen in a little dish after dropping some in for the Betta. While the Betta was finding the falling food the ADF were eating in the dish.
As BettaloverSara and give them a few days to settle in. They've never seen plants, never lived with other fish, etc.. It's culture shock.
PS: You can also take a clear plastic pipe (like on the end of a siphon), place in the dish and drop the food through the tube. When I did that I would feed the frogs first; hold on to the tube and feed the other fish in the opposite corner. Lift the tube as you're feeding the Betta.