Stick with the flakes, suppliment with some brine shrimp, and occasionally bloodworms. Angels tend to go mid to top, but will pretty much go top to bottom. Zippy fish tend to hog the food from angels, try putting some flakes in the stream of the filter to shoot some of them to the lower levels of the tank. It's not unusual for any fish to refrain from eating after being introduced to a new tank. I have yet to see a healthy angel starve to death, once they settle in they eat like pigs.
You should have some sinking food, as well as bloodworms for the corys. They will eat the leftover flakes that hit the bottom, but require a little more protein than most flakes provide.