Water cloudiness/Current health status

[CaptainMako]

Hey all.

So I have six lyretail mollies in a 29 gallon aquarium. It's a quarantine right now before they go into another, cycled 29 gallon with the rest of my mollies. Big for a QT, but I'm turning it into a saltwater later.

Anyway, I had a problem with unknown tank cloudiness before. Tried looking for help here but received none, worked the issue out on my own.
I think it was the filter cartridge falling apart slightly, as I had cut the side of it open to remove the carbon.

The problem is back, but this time the water is littered with a trillion tiny particles. I don't know if they are bubbles, but they don't look to be filter pieces or leftover food. Does anyone have an idea what it is.

To the subject of the actual fish, I need some help as to determining their health condition. I purchased them from Petco (Only option), and all six were in the same tank together with no others. Just come concerns.

1. One molly is easily identifiable as the weakest of the group. He isn't as colorful, spends most of his time with his face shoved against the heater, and is slightly "limp" when he swims. I do not think he has a broken back however. The tank is at a perfect temperature and I always watch to make sure he eats, but still. Should I be concerned about him?
2. Last night I noticed that some of them swim in place for short periods of time. The flow from the filter is not excessive what so ever, isn't this a sign of ich or something?
3. Another one of the mollies (it could be several, they all look alike) has small black particles near his tail, on one side. They aren't large at all, and there's only a few. Probably just me overreacting, but should I watch for anything?

The mollies have about two to four weeks left before the quarantine is "finished". The last addition to the cycled tank is intended to be a gourami, but I will deal with that later. The new mollies, or the tank they are in, have had next to nothing to do with the cycled tank, so nothing has spread.

Thanks,
-Shaun

 

[HUKIT]

As far as the cloudiness what color is it, green, brown, or white? Maybe they are microbubbles, is there a airstone near the filters intake tube? What kind of filter is being used?

As far as the fish, I'm assuming the QT is cycled and water conditions are in check, specifically what are they?