I have a 29 gallon tank that has been doing really well for months, last week it started getting somewhat cloudy, did a partial water change and it was fine for a few days but started getting greenish/cloudy again relatively quickly. During this time I noticed the rasbora had a sore on his tail and I thought he had been injured during the water change somehow. Last night he died, and today when I checked on the tank, three fancy guppies except for one have died in a 6 hour period. . I still have one female guppy, 1 rasbora a bleeding heart tetra, a rainbow tetra, and a (not sure) white finny tetra, a betta, a catfish, and a bristle nose plecostomos and five neons. So far everyone looks ok, but the neons look distressed Any ideas to what might have caused a sudden death? I am very sad, three of them were babies I raised this year. Thanks in advance for any insight.