Planted Tank Enthusiast
Join Date: Jan 2013
Location: Baton Rouge, LA
Before adding any new occupants to the tank, especially after a sickness or problem with existing tank, I QT newcomers for a month. Any fish that shows aggression or fin nippers get separated or yanked ("bad seeds" can show up in the mildest species). Crowded conditions and an unruly occupant stress fish, leaving them open for disease.
Flashing, rubbing, itching and scratching could be caused by parasites, which can cause dropsy and bacterial infections.
Camallanus worms sound like the culprit. Females can die after giving birth (usually only a few fry), fish generally waste away, bloat and die quickly, and it is often misdiagnosed as "livebearers disease". I would rule that out before replacing anymore fish.
Your fry will get eaten by the neons and guppies. If they do make it, they will get the Camallanus worms when new eggs hatch. I don't keep shrimp, so I don't really know first hand the effects on shrimp, but the neons are a good candidate, too. Basically, no fish is immune to an infestation. When treated early with levamisole, the fish pass the worms and recover, unless they are really diabilitated. Then you must treat again to destroy the eggs.
I went through it a few years back, early in my guppy keeping, and it was a very frustrating ordeal. Almost turned me off aquariums. Now, with QT procedures, and knowing what to look for and how to cure it, I haven't had a guppy death (other than natural causes (old age), a couple jumpers, and fry munchers) in OVER 3 YEARS.
Some of them are housed with other fish, especially Neon Tetras.