Guinea pigs scratching nonstop?

Sorry if this is a long read but with all my other questions I’ve posted in the past I try and put every detail I can in my question, to ensure that I can get the best answer.

So, I have another problem with my guinea pigs.

I have two guinea pigs.

One is Nibbler and the other is named Mickey.
Nibbler is a English crested piggy. He has a brownish coat with a white face. Mickey is a abyssinian piggy. His body is 95% white and his face and ears are black.
A few weeks ago I posted a question about how to make them stop fighting eachother. Well I’m happy to announce they managed to stop fighting on their own.

But a new problem has occurred, they’ve been scratching nonstop. Another thing that is concerning is that they sleep a lot now. As of right now they’re sleeping instead of playing like they usually do in the afternoon. This really worries me but I think its because they’re always scratching.

Earlier in the day when I woke up I picked up Mickey and checked his body and he had a crusty mouth this concerned me. It wasnt red or anything like that. I started gently scratching the crust off from around his mouth. This set off a panic in me and after I put him away and washed myself I went hunting on the internet to see what it could be. After some time hunting I went back to check them for anything else I could find. This time I started with nibbler because I didn’t check him after I checked mickey the first time. I looked and looked and pushed his hair around and I didn’t find any red patches of skins, or sores, or rough scaly patches anywhere. But I did find small little yellow patches on one of his hind legs. They kind of look like scabs but are healing. That’s it I didn’t find anything else on nibbler. After, I finished checking nibbler I went and checked mickey. I repeated the same steps I did earlier. I also went back and checked on how his mouth was. I pushed his hair around and looked and looked and again I didn’t find anything on him except for a single yellow scab, this time on Mickey’s tummy. The crust around his mouth was gone and his mouth was clean of any sores or yellow scabs.

Neither of them have sores, red irritated skin, rough scaly patches, missing hair, none of that. All they have is the little yellow scabs.

I took them to the vet a couple weeks ago because they both had a cold. I’ve been giving them their medicine (trimethoprim-sulfa) daily twice a day as the doctor prescribed to me. So after searching on the internet I’ve come up with two conclusions: mange or ringworms.

If its mange I need to order Invermectin dewormer horse paste (I know it’s intended for horses but I’ve read reviews online and its great for guinea pigs and other small rodents that have external parasites). If it’s ringworm I just need to keep giving them their medicine and buy an antifungal cream.

So I guess my question is which do you think it could be. I’ve seen pictures online and to me it looks like it could be ringworm. Which can be passed to humans as well. I’ve been careful and always wash my hands after touching them. I’ll try and add some pictures later to show exactly what they have.

I would like to thank you guys in advance for reading my very long story. And my piggys will be grateful too once I find out exactly what is making them so itchy.