Sick Dark angel - Cichlid

[tmf]

070209
Recently noticed that one dark angel was not as interactive with the other as usual, and it developed one small dark spot on its body, of the same color as it is. It also has been glancing for a while. I never thought too much to this because other than that, i could not find anything to really work on. I knew nothing of glancing at the time.
This evening however, things have seemed to have become more serious. I noticed that on it's right eye (same side that has developed the spot) is some cotton hanging off it. I have no idea of how to treat this, but will more than likely begin with Melafix and/or Pimafix in quarintine.
It is also fighting alot with other fish, and never used to before. It shakes every now and then also.
Other than these major symptoms, it is still relativly active.
I have also noticed today that all my other cichlids have begun glancing, the red pecock, franticly at times.
Something is wrong with my water obviously, but i have no test kit other than a PH test kit. I have added ammonia remover and activated carbon to a filter in hopes that it helps.
Their is small particals floating around, though have not noticed it before, and the substrate gets covered in crap quickly due to the mixture of fish and feeding. Syphoning is missed in one section of the aquarium due to the thickness of the plantation. I am asuming that the floating particals is due to the filter's power pushing it around at that these types of filters squash the sponges so to that some of the crap passes right through and also due to the fish stiring up the substrate.
I recently lost an electric yellow that was seriously distressed.
Where to go from here, am i going to lose the rest?
Could the cotton stuff have come from my corner filter or a developement of a disease?
Am i just killing my fish?
I have been over cleaning the aquarium and filter destroying all good bacteria, i have only realised and stopped this within the last few days though. Is it too late for me?