Angelfish, Columbian Tetras And Weather Loaches

[ninjacheesefish]

So three things really:
1) my columbian tetras have this weird disease. They first get black scales on their body, then they swell and then they died. I had 12, now I've got 6 any ideas? (See photo it's on the underside)
2) one of my angelfish has a swollen stomach, eating fine behaving fine. Dropsy or just over eaten?
3) how do you sex weather loaches? I have two and don't know what they are...

I've attached some photos in case. Sorry for the bad quality. Any ideas would be great thanks.

 

[ninjacheesefish]

Any one got any ideas?

 

[silenthawk2x3]

Weather loaches are hard to sex by yourself if you don't have a whole bunch of them to compare them to. I have 2 males that are about 8 inches each. Usually females are plumper than males, and males sit up on their pectoral fins which are slightly more pointed than the females rounder ones.
As for your disease I'm not particularly good at identifying specifics other than its bacterial/fungal/parasites. Also it might just be me but I'm not seeing pictures or links to pictures, sorry.