For future reference, wrasse are commonly “Typhoid Marys” that bring ich and velvet and other parasites in to the tank. This is especially likely and common with visual observation quarantine.
This because they have very thick slime coats, sleep in mucous cocoons and/or under the sand. This keeps them safe from low level parasites but they still often harbor them, particularly in the gills. So an apparently clean fish that showed no symptoms in qt for months often brings in even serious parasites like velvet.
I’ve actually had velvet and ich in my wrasse tank and many of my wrasse thrives in “velvet management” which is insane to think about for many, but it shows me just how resilient they can be. I lost a couple fairy wrasse but about 75% of them adapted, I lost no halichoeres nor leopard wrasse. A penciled wrasse was unable to survive. Of course, I didn’t realize it was in there until it took out a butterfly I added. It quickly succumbed and everyone survived another year until a power outage occurred while on vacation and I lost about 50 fish in various systems. Very sad. In fairness, I did quarantine those fish a good month before they died in quarantine under my fathers care.
I don’t recommend anyone try to replicate this I see it as unethical and I’m not proud of it.