I am starting to see many dead bees around the entrance, and suspect something is wrong.
Is it warm enough where you are to inspect the interior of the hive?
If the weather is sometimes warm, sometimes cold, you will see dead bees around the hive, those that are old and just didn't make it, or bees that went out to "cleanse" and didn't make it back because of the cold.
If it's spring in your part of the country, are you feeding yet?