Are they scared and timid yet? Given you just got them, they may be uncomfortable going into open water to feed. Now on the other hand, it may be possible they don't like your food, although I use the same flakes for my angels, it still is a possibility. Give them a little bit of time, and if they continue to not eat it, maybe try something else.
try them on frozen(or live) blood worm they love it did the angel have damaged fins when you purchased it?what is in the tank with them?
If they don't eat bloodworms or brine shrimp, something is up. I'd give them a couple more days though, your water may be quite different from the water they were raised in. What method did you use to acclimate them to the tank, and what is your water temperature?
Tolak
The pH & hardness of your water could have been vastly different from what they were raised & bagged in. Sometimes pH shock takes a few days to show up. If they are ok after a week they should be fine in this respect.
I would bring the temp up some, I keep my smaller angels around 84F, larger ones usually a little cooler, 80 to 82F. This means around 27 to 28C. A little heat helps stimulate the appetite, when they are hungry enough they will eat the flakes. Mine eat anything I toss in the tank.
Tolak