Both. Being new you tend to worry about things that are not a problem. But if you have worries never be afraid to ask. You don't know if it is a problem or not. You don't want your chickens harmed because you are afraid to ask.
Expect them to go through another juvenile molt in another 6 to 8 weeks. That's when they will get their adult plumage. Most chicks will mostly have their adult feather colors during their juvenile molts but I've seen some that had some exceptions. Personally I would not be concerned about it. What is important is how they feather out in adult plumage.
I've seen adults change their feathers when they went through an adult molt, after they were adults. The plainest example was a hen that had a Mottled pattern molted and came back as an Exchequer when she was a year and a half old. A beautiful pattern.
Then there is the concept of "leakage". Even breeders can have this happen. That's when feathers of a different color leak through the plumage, generally a recessive color hiding in the background. I've had random gold feathers on what should have been a solid black rooster. It is pretty common for white chickens to have a stray black feather, sometimes several black feathers. Or red.
There are different things that could be going on with your chicks. I do not consider them a health problem. It may sort itself out in their adult plumage or not. I don't know how big of an issue that may be for you but it is pretty common. Good luck!