On Mar 4, 7:19�am, "avgeek21" wrote:
It's a 6 gallon tank and I change 2 gallons every 2 weeks. *Even with
all the plants, with 6 fish my nitrate level does run in the 45-50
range and I've always worried about that, but the fish seem to do
fine. *I have not changed or added anything recently so I think I can
rule out a parasite. *I looked closely and noticed that one Harlequin
rasbora (over 1 year old) is also looking a little pudgy. *Thanks for
the help.

Your problem most likely is not enough water changes.
Start doing a 20% water change weekly.
You say your fish seem to be doing fine, yet they aren't.
They are showing Dropsy symptoms which the #1 cause is poor water
conditions.
Sorry if that sounds harsh, (not trying to be).
You may have heard of "New tank syndrome", well there's also "Old tank
syndrome" where the nitrates get too high and start killing off fish.