OMG, that is such a heartbreak.
I don't expect I am being any help, but I hope this will, finally, clear up fast.
Were the guppies home bred?
Sometimes resistant fish can carry contagion which doesn't noticeably affect them, but is then present when other fish become susceptable, as when stressed by a move.
I had recently come across some references to parasites/disease which can cause skin to peel.
And as 'cotton wool' fungus showed on some of your fish, the problem could be fungal all around, unless one affliction is secondary to another, and it does sound possibly parasitic, especially with the guppies picking at the skin of affected fish.
I couldn't remember what and where the most likely references were, but just Googled a bit and I'll plunk the assortment here just in case anything might help.
Even elimination may help narrow the field.
Would Velvet show on neons?
It's said to often be hard to see, and what with some of your fish having skin peeling...
[URL="http
/www.oneworldinternetcafe.com/betta/...h_diseases.html"]http/www.oneworldinternetcafe.com/betta/...h_diseases.html[/URL]
... Oödinium is one of the more common diseases in cultured fish. This tiny parasite is capable of decimating an entire fish population, usually before you realize what the problem really is. It strikes both fresh and saltwater fish equally.
In freshwater fish Velvet is caused by either Oödinium pilularis or Oödinium limneticum. In marine fish Oödinium ocellatum causes Coral Fish disease. All three species are similar to the well known parasite, Ich.
Oödinium uses flagellum to adhere to fish and then forms rod pseudopodia which penetrates the skin and gill filaments. This destroys the cells and allows the parasite to feed on the nutrients inside. Eventually the parasite matures and divides into dozens of cells that drop off the original host and spread out in the tank in search of new hosts to feed on. They will die within a day if they fail to leach onto another host. They produce a white pustule on the host not unlike Ich but much finer. Sadly they are usually not seen in time and the host dies. Also, not unlike Ich, they are a common occurance in most pet store tanks but only become lethal when fish are stressed. (Poor water quality, temperature changes, handling etc.)
Symptoms:
Fish will scratch themselves against hard objects. (Trying to dislodge parasite)
Fish becomes lethargic
Fish display a loss of appetite.
Fish loses weight.
Fish displays rapid gill movement. (a universal sign of illness)
Fish clamp fins against body.
Fish developes a yellowish or rusty colored film on its skin. (telltale symptom - though hard to detect, try a flashlight beam on the fish in a dark setting. Look on the fins and gills.)
Fish's skin will eventually begin to peel off. ...
[URL="http/www.myfishtank.net/forum/disease-fo...am-worried.html"]http/www.myfishtank.net/forum/disease-fo...am-worried.html[/URL]
... Well two days ago, I noticed a female platy (that I thought was pregnant) had white sides and clamped fins. The white sides on the sides is a tell-tale sign of a flexibaciter infection. I immediately quarentined my platy, and began medicating with triple-sulfa. Tonight when I came home, my other pregnant platy was stricken with the disease. Her sides looked like the skin was falling off. Again, tell-tale signs of flex. ...
... The two fish in quarentine definetely have flex, as their skin is "peeling" off. But the other two that are now sick only appear to have "body fungus." I am assuming that this is bacterial infection since I do two water changes a week, and nitrates never get above 5. ...
[URL="http/answers.yahoo.com/question/index?qi...28130450AA6hlcT"]http/answers.yahoo.com/question/index?qi...28130450AA6hlcT[/URL]
... Well, the only thing I can think of why a Betta's skin is peeling is a possibility of fungus growing on the skin. ...
[URL="http/guppyplace.tripod.com/Parasites.html"]http/guppyplace.tripod.com/Parasites.html[/URL]
... Guppy Disease
There is actually a disease caused by a protozoan that is more commonly seen in guppies than in any other fish. This is a tiny parasite that attacks the skin and may even reach as far as the muscles or bloodstream. They may get large enough to resemble ich and the scales may protrude, swimming is difficult and the skin usually falls off as well. If this is not taken care of quickly it can spread throughout the tank and be very difficult to control. ...
Since this can affect other fish but more frequently occurs in guppies, one wonders...
I so hope this is worked out fast, and that the rest of your fish will be OK.
Have you posted in the emergency section?
Maybe Wilder or some other expert will show to cast an informed eye on the situation, but the post heading only suggests a possible ill and they wouldn't be specifically looking here for anyone in need of their skills.
If you haven't already done this, a more specific thread in the emergency section might produce some useful answers.
And if sympathy helped, you'd never have lost more fish...
Edit - are the baby guppies in there because you cycled with feeders?
Because they're notorious for having been raised in poor conditions and carrying disease as a result.
And that could explain everything, including the shyness which can often be a sign of disease.
