wiggling

PLS REFER TO THESE VIDEOS TO GET THE CONTEXT This molly started wiggling like this...then all other mollies started wiggling(THE SAME CORNER!!)....then all of them started to die back to back without a sign (sudden deaths....just fine yesterday,..found dead today morning)....this happened like...

Hi everyone,   I'm just desperate for some help. I have a 60 liter guppy tank. Right now I have about seven adult guppies and some older fry. Slowly, about every week or two weeks one of my guppies dies the exact same way. It's only been females. They start looking very thin and emaciated, they...