I had never heard of Health Extensions before. It looks to be a pretty standard and decent food, comparable to other options that are more commonly available. $60 sounds like a lot for a large bag compared to what I'm seeing it go for online at places like PetFoodDirect etc. so you might consider price checking online if you're looking to save some money. RC would be a a little pricier but many people on YT have had great success with this brand and many breeders use/recommend it.
But if you're happy with the Health Extensions and your puppies are doing well on that, I'd probably stick with that food until the pups get older and transition to a different formula.
I recently bought a small bag of a lower fat RC kibble to mix with some of Toki's higher fat canned foods and she's doing really well with it. I guess one down side to RC might be bag sizes. I actually like that they sell the small breed formulas in 2.5 to 3 lb bags (Toki eats mostly wet food and we don't go through very much kibble with her) but then the next biggest size is a 10 lb bag which is way too much for us to have open at one time (it may not be an issue for you if you're going through a lot of it with your pack though
).