welcome to ReefBase
Yes it's a real PITA. Unfortunately ich is fairly common. A lot of shops run UV/hyposalinity which suppress the disease but don't fully cure it. Then as soon as the fish go into your tank, the parasite is able to reproduce again.
With velvet the spots sometimes have a slightly browny/goldy colour to them and are fine, with ich the spots are usually more pronounced. Your pics look more like ich to me. Hopefully somebody else can verify. ( @HK_Fuey @Gav
Even if it is just ich and not velvet, PolypLab Medic may not be strong enough to cure the fish completely, so be prepared to take them out and treat with Seachem Cupramine or similar if they deteriorate. Clownfish are fine with Cupramine, if you have other fish, do check on google that they can handle copper. Done properly it will permanently solve the problem, but copper in general can be quite hard on the fish.
The other thing is that the parasite is now in your display tank, so if you treat them and put them back in, they will likely catch it again. The only way to be 100% sure to avoid this is to leave the tank empty of fish (called 'fallow') for 72 days or more. This used to be 3 weeks when I started in the hobby, it seems there are more resilient strains of ich about now.
PS. if it is velvet, then leaving the fish tank dark can help