As your boys have it in several places, it means long term exposure to it; the time between infection and outbreak is 10-14 days. Each infection spot means a spore has got to your piggies. With so many spots at once that means bad hygiene and a long term untreated problem with spores shed literally everywhere. Normally we only see piggies with just one acute spot; more develop with the creaming method, which only addresses acute areas (and then only part of them) but not any there places on the body where spores can have got to and cause secondary infections in due time.
It is rather safe to assume that the breeder is simply out for the money but not bothering about vet care. Did you actually see the premises and other piggies or were your babies just handed over?
Sadly anybody can call themselves a breeder without licensing and any welfare control in place. The same goes for rescues, hence why we have a rescue locator for those vetted good standard rescues with mandatory quarantine and vet care that are by far the safest place to get guinea pigs from that do not come with nasty surprises.
If the breeder is not prepared to cooperate and is trying to wiggle out, you can report them to your local council over trading standards - if they advertise their guinea pigs for sale in some form, then they fall under that category.
I am very sorry that you have such a tough start. Because your piggies have several affected areas, the best method would be to treat orally in order to make sure that you reach all nooks and crannies. Use two baths, one at the start and one at the end to wash any spores from their coats. And please make sure that you yourself and any person handling the piggies is having an all-body nizoral/anti-dandruff shampoo themselves in order to prevent coming down with ringworm themselves. It is not pleasant at all, especially in children. All these aspects (and more) are detailed in our ringworm hygiene guide to help you make sure that you deal with ringworm only once. It is going to be a tough couple of weeks, but if you do it right, you can get past it once and for all.
I have used my own advice a year ago in a room with 30 piggies and have managed to contain the infection to the one infected piggy, so it can be done!