I have a 55 gal with variour cichlids in it. Son cleaned tank as usual then a few days after put a few goldfish in there. I took them out as soon as I noticed them. ugh! All was going good but then they began to die off. Had him change tank water with the first few that went, but had 4 more lost last night. They all look healthy except a little sluggish, scraping rocks, and most are staying at top of tank. Please help fast, praying for a miracle.