On 4-9-2021 my Sailfin Tang in photos attached showed up with tiny black spots and by 7-9-2021 they turned white and after doing a freshwater bath the spots seem like they are gone. The Unicorn Tang in the same tank showed up with a slightly frosting on one eye which now seems swollen. Both fish are in the same tank with corals, snails, hermit crabs that have shown no signs of issues. I did also have a small pair of Picasso clowns, pair of cardinals, bi-coloured bleny which were in the same tank but all died within the last 2 weeks on seperate days. All fish have been eating as normal. I did notice the Unicorn tang swimming against the flow for around a month or 2 prior to noticing the black spots. What is happening and what should i do to save these guys and the tank.