Sick cherry barb?

[karen99]

I have an old cherry barb who I recently moved into a new, heavily planted tank. He seemed to be very happy and active in the new tank. I waited about a week or so and everything seemed fine, so I bought five baby cherries. After I put them in the tank, I noticed one of the babies seemed to be acting funny. i decided to just wait and see what happened.
Well, now the older one is acting like that. And I'm not quite sure what happened to the babies; I can never see more than one at a time - either some have died and been eaten or they've found themselves very good hiding spots in all the plants.
The older one is behaving strangely. First of all, he has become extremely shy, darting into the plants at the slightest disturbance (he didn't used to act like this). He also spends most of his time in one spot, tipped slightly head down, fins folded tightly against his body. Occasionally, he will sort of give a sudden twitch and flick the fins open for a second. He looks ok otherwise, and still has his pretty deep red color. He just isn't behaving or swimming around as usual.
The other (non-cherry barb) fish in the tank are behaving normally. Tank nitrate/nitrite levels are good.
Any ideas on what the problem could be?

 

[karen99]

Update - I did a partial waterchange, hunting for barbs in the plants. Of the 5 babies, I found one dead and one dying and unable to swim, (which I removed to a bowl, though I don't expect it to survive), and two that seem quite sick, but still able to swim so I left them. The adult also seems weak.
They appear to be gasping or gulping - they hold their fins tight except to flick them out rather violently with each gasp. One of them is actually fluttering his fins rapidly, while staying in one spot. They aren't at the surface; just hiding in the plants.
Sometimes they roll a bit to the side as if it's difficult to stay upright.