Sometimes the ick doesn't produce very much and they will only have a few spots. I treat ick by raising the temperature of the aquarium
(this will speed up the life-cycle of the parasite, and possibly kill some as well). I combine this with aquarium salt for 2 weeks with large water changes every day with a gravel vacuum(
the parasite hides in the gravel, but sometimes can be seen swimming if you have a good eye). If you are doing a water change in a small aquarium like a 2.5g it's best to do daily 100% water changes - Bring the entire tank to a sink or tub and rinse the rocks really well several times to remove all parasites. It helps if you remove everything but the rocks then stick your hand in the rocks and swish them around really good. When the above treatment fails, I have found that coppersafe works the best.It's best to avoid using medication first thing as it allows the parasite to build a resistance to the meds, then they may not be as effective when you really need them.
Make sure to check your nitrates, they are often the cause of a ick outbreak.
Here's some images of what Ick looks like, it can sometimes be smaller or bigger
Bettas with Ick