Welcome to the forum Mcedwar! Glad you joined us.
I may be missing something, but I see queen cups, which are empty, not capped queen cells. Queen cups are common. The bees are being prepared. I see capped brood and larvae in your pictures as well as some drone brood. So, it looks like she is doing her job.
When you say empty frames, do you mean frames where there is no drawn comb? Before putting another brood box on, I would let them draw out 7-8 frames, with comb, first. Don't give them more space than they can handle.
It looks like you are still feeding sugar syrup. That's good. They probably need that to draw out comb.
There are a lot of bees on the ground in your first picture. Before placing frames on the ground be sure you know where the queen is. She could get stepped on down there or get lost. When working a hive, I like to turn the lid upside down. Then I check the inner cover to make sure the queen is not on there and set that to one side. Then I place an empty brood box on top of the upside down lid. As I inspect frames, I place them in the empty hive body. I keep them in order so that I can return them in the same order. I try to keep the brood frames together. Should the frame with the queen on it get moved she is less likely to get lost or damaged. Everybody has their own way. That is mine.
