A tang, overnight?
I have a big tomato clown that has the same powdery look. The clowns fins look frayed and it has a white dusting mostly on its head between the eyes. The Niger Trigger has what look like white cysts on its eye and a light dusting on it. The Hawkfish, blue head wrasse, and lawnmower blenny show no signs at this stage. I have been told ich, Brooklynella, and velvet disease.