If an Ericaceous plant is blooming well and growing normally, there's no reason to fertilize it. Plants are not like humans needing regular 'food'. Now if you are on sandy soil in the high rainfall Southeast, they are more likely to possibly need fertilizer, but even that is not a guarantee.

I am in very completely sandy SE coastal soil. They are doing well but with the sandy soil it just makes me question if they are getting the actual nutrients they need. And I am not looking to fertilize every 3 month or anything, just wanted to know if once or twice a year was a good idea for them, especially since they are new.

Ok thanks for clearing that up - I am now planting certain rhododendrons on mounds of pure sand. I am not fertilizing them their first year, and they are growing fine. The heath family prefers infertile soil, but that isn't to say your notion that you have to make up for leached nutrients is wrong. Just go easy on it.

FYI 98% of wholesaler produced plants are as replete with nutrients as they possibly can be when entering the retail trade, and in fact many of them have Osmocote beads added to the potting soil that will keep them "fed" for another year. I really think there is never a justification for fertilizing something newly planted. You want the plant to form roots to among other reasons, seek nutrient rich(er) soil. Except in the very rare case of plant families that are absolute nutrient hogs like Brugsmansias and maybe a few other tropicals. Talking ornamentals of course, it's completely different w/vegetable starts, those wholesalers do not waste the money on added fertilizer beads.

I have heard that coral bells thrive on neglect and only about one watering per week...if they are doing well, I wouldn't touch them.