Check that sealed brood is worker, not drone. Check brood pattern and quality of larvae.
Check for stores, if they don't have enough to eat to support the growing population you may need to feed them for a while, but you need to be sure the queen has room to lay.
Check also for signs of varroa and disease, as well as damaged combs that may need to be replaced.
The first inspection of the year can yield quite a lot of wild or brace comb, so have a plastic box handy to put it in.