All my panda platys died over the course of a year--dropsy?

[Captain Stress]

I have a 36 gallon planted community tank that has been established for nearly two years. About a year ago, I purchased five panda (black and white) platys. They thrived, even bred some offspring, which added two additional members to the school.

Within about three months, the largest developed pine coned fins in the black rear part of the body. It lived like that for several weeks, then fins started wasting away until it couldn't swim well and died. Eventually, the same thing happened to all of the other platys, but almost sequentially. It took nearly a year for them all to perish.

Was this dropsy? I have other species in this tank (cherry barbs, rasboras, bolivian ram, and others) that were not affected.

The black fins puffed up. Then the fins started wasting away--all very, very slowly. The fish acted completely normal up until the last few days.

Picture attached of the last victim.

Tank parameters:
Ammonia 0 (or very close to 0)
Nitrite 0 (or very close to 0)
Nitrate (Med--goes down after weekly water change)
pH 6.5 (My water source is 7, but it always goes down to 6.5)

 

[Fishies86]

I'm not 100% sure from that picture but it looks like it may have been dropsy. Did it look like it was wearing a really frilly dress?

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[Captain Stress]

Yes, fins were "pine coned" out, especially in the rear part of the body, except it was for weeks, sometimes months with the fish acting completely normal. Then the tail fin would start to disintegrate and finally the fish would start to act dopey, floating around the tank strangely for a day or two then die.

I guess this is dropsy from what I have read. It only affected the platies, though.