You can reclaim any vet cost from the pet shop you bought your piggies from if it comes up within 2-3 weeks of purchase in the UK or 1 month in the USA or Canada as part of your customer rights for having been sold faulty ware as exposure and infect must have happened at the shop. More details in this link here:
New guinea pigs: Sexing, vet checks&customer rights, URI, ringworm and parasites
Please be aware that ringworm is highly contagious and is the single most common problem to jump species. the invisible spores can stay viable up to 2 years and they are shed in their thousands in an acute outbreak. A vet grade disinfectant, utmost hygiene and the proper treatment are absolutely crucial in not turning this into a long running saga. Ringworm is not the problem you can get away with skimping.
Please follow the advice in our very practical step-by-step hygiene guide. I nearly 15 years of existence we have had time to find all the various ways of how ringworm can be passed on and passed back - and also how to address every possible angle. It is much easier, cheaper and less frustrating to do this properly and get past it in two weeks once and for all.
Here is the link again:
Ringworm: Hygiene And Pictures
PS: It would help us to help if you please added your country to location in your account details (accessed via clicking on your username). We have members and enquiries from literally all over the world with very different climates, backgrounds, vet access and medical brands, all of which we can take into account when personalising an answer. otherwise you'll get our basic standard response. Thank you.