You may have a few options, depending on what your feed store carries. The normal progression is to feed them Starter for the first 4 to 8 weeks, then switch to Grower. After they hit 20 weeks or start laying, switch to Layer. But there are a lot of other products available. The main difference in any of them is the per cent protein available, except for Layer. Layer has additional calcium for laying hens to use for their egg shells, but that higher level of calcium can hurt growing chicks. So don't consider Layer until they are ready for it.
Some of the options and the per cent protein available are:
Starter - maybe 22% to 24%
Grower - 16%
Combined Starter/Grower - 20%
Grower/Developer - 15%
Flock Raiser - 20%
These per cents might be off just a bit and the actual product might be called something a little different depending on the brand, but these should be close. I'm also ignoring the Game Bird feed which is not for chickens. I've used the 24% GameBird as a Starter when I raised turkeys with the chicks, just not for many weeks. You can be pretty flexible with the feed.
Other than the Layer, the rest can be used about anytime. The general ideal is to start them on something a little higher in protein for their first few weeks to help get them started and feathered out. Then drop back some while they continue to grow, but don't overdo it. Sort of give their skeleton and internal organs a chance to keep up with their body growth. That's wherer the 15% Grower/Developer comes in. It has plenty of nutrition for them to grow, but is generally recommended for after 13 weeks age.
What you can do is not as restrictive as it sounds though. Chickens can handle quite a variety and handle it well. The main thrust behind the normal progression is that this is what the commercial operations do. They are feeding thousands at a time and this is the most cost effective way to do it.
You can feed the 20% Starter/Grower the entire time until you switch to Layer. You can use the 20% Flock Raiser instead. Or you can feed the 20% until you switch to Grower or Developer. You don't even have to switch to Layer when they start to lay. Just continue with Grower or Flock Raiser and offer oyster shell on the side. You have a whole lot of options.
This is a long-winded to say to not get too hung up on it. In your specific case and not knowing what options are actually available at your feed store. I'd suggest maybe one more bag of Starter. They will eat more as they get bigger so it probably won't last as long this time, unless you start free ranging them so they can forage for some of their food. See, still another option. But when this bag of Starter runs out get Grower, the combined Starter/Grower, or Flock Raiser. It really doesn't matter which. Or you can swithch to one of the 20% options now. I just would not drop to the 16% or 15% options quite yet. Get them feathered out first, which should be by the time they are 5 weeks old.