I have an ORA Harptail blenny in prophylactic QT that looks like it is almost dead. Seachem badge shows no ammonia, nitrates tested at 6.8 last night via Hannah colorimeter. Slowly raised copper to 2.5 over the span of about 10 days and we are on day 9 of copper. Last night I added my third dose of metroplex as directed (2 even scoops for 20 gallons). Three other fish look fine. He was looking as good as ever last night. What do i do?