Good morning!
Since the chick is eating and drinking.. it may just be a tad hot causing the heavy breathing. Be sure to keep an eye out for pasty butt.. as while many folks will swear it's caused by too hot of brooder... I HAVE seen it in broody hatched/raised chicks. The truth is it can be caused by any stress factor which could even be internal that we cannot see or assess... such as under developed organs, etc.
The thing about a chick that seems slower than others... it's the weakest link and will likely be the first to go IF there were a predator attack or illness/parasites, etc. These chicks may never catch up or be as strong as their brood mates. Even when everything goes right during incubation and hatch... someone HAS to get the cruddy genetics sometimes.
For ME (everyone has different situations).. I actively breed my birds with intent to improve or maintain my genetics.. So this chick would be on the short list to head to freezer camp once big enough or selling if it lays eggs well... as I don't want this type of weakness breeding forward in my flock. It's a hard line to draw... but ultimately any weakness invites predation and disease (internal and external parasites) to flock... survival of the fittest here.. TO a point. All are provided for very sufficiently. Nature, though beautiful can be quite brutal ultimately.
If you want to provide a boost to the overall immune system consider offering Poultry Nutri Drench in the water or Rooster Booster brand Poultry Cell product mixed into mash or on a treat... just to make sure they're at their full potential nutritionally... since that's the very base of all things health, after genetics. No supplement should be given more than 10 days in a row.
These suggestions and thoughts are presuming that you are using a flock raiser, all flock, or starter type feed that is adequate for the species and age you're working with... with oyster shell on the side for active layers if you have others.
Hope this helps answer some questions without being too negative. Please feel free to ask more questions if needed. Pics always welcome!