Once you run a quality skimmer, you will see just how bad those guys are. But there are some mods you can make to them to make them run a little better.
Also damsels are some of the worst fish you can start with because they are essence of pure evil. They are well known for bullying any fish you add after them, often to death, even if the fish is much larger than they are. They are also a major pain in the ass.
Next, do your research before you buy a fish and dont trust what the LFS has to say about them 100%. They are well known for giving bad, misleading advice, because at the end of the day, they are there to make money off of you. Anyone one on here would have warned you not to get the damsels and would have guided you towards a much better purchase.