[Delta Bay]

I would put the baggie right under the cluster. I don't know your location but in my location packages have starved with the feed on the opposite side of the follower. Sometimes the bees just don't know how to find the syrup if it gets cold when it is just outside their reach. Make sure it is good and warm and have enough of the syrup outside of the baggie that will lead them to the source. There is no reason they shouldn't be taking it.

 

[Delta Bay]

How do I know if they are starving?

I don't think your bees are starving. I was just giving an example of what has happened in my location to more than a few beekeepers that thought there was lots of flowers around. They don't always starve. Sometimes the population can drop down to critical numbers before they can get establish.

The reason for feeding a package that needs to build new comb is so they have the resources to do it quickly to have the replacement bees that will need to take over the duties from the decreasing number of original package bees. There may be enough forage for them in your location but still it is in the best interest to the bees to make sure they are not taking the syrup because they just don't know it is there.