I agree on ich and paraguard not effective nor recommended.
You will need to place fish in Quarantine tank and treat with Coppersafe or Copper Power at therapeutic level 2.25 for a FULL 30 days (do not interrupt this 30 day period) monitored with a Hanna Brand copper test kit- No API brand. Also monitor Ammonia levels while in quarantine with a reliable test kit and add aeration during treatment using an air stone. All other fish in with it should also be removed as they have also been exposed to the parasites and placed in quarantine tank.
The display tank will have to be kept fishless (FALLOW) for 6-8 weeks to assure the existing parasites go through their life cycle without a host fish and die off. Inverts and coral can remain in the display (not treatment) tank during fallow period.