Conditions What could this be?

I have two guinea pigs and a question for each.

My first pig is a long hair and I was recently trimming him and I found greasy-feeling areas, which -when i looked closer - had black dandruff looking stuff coming off his skin. I looked really close and they weren't moving as far as I could tell. I gave him a bath and trimmed those areas very short, so I could really clean him off. I'm hoping it was just dirt or dry skin, or even caked-on dry poo? Since I did this about a week ago, I've checked and it hasn't come back. Also, my second pig doesn't have it so I was hoping that would stop the chance of it being mites or a fungus. Any advice?

The second pig is generally healthy and this may be nothing but I thought I'd ask. I just gave him a bath just cause it's been a long while since, and as per any guinea, he freaked out a bit. Safe to say, he probably got a little water in his face. When I was blow drying him I started to notice him sniffing really loud. I never noticed it before today. It wasn't constant like it was his breathing, it was when I would put something (like my hand) in front of him and he would sniff. It was very loud, I was sitting with my legs crossed and I could hear him from down there. I don't know if it's just the water or I should be worried about a respiratory problem? I haven't noticed any sneezing, wheezing, or eye problems though.

Please help with any advice! I don't feel like they need a vet trip,so I just want to see if these symptoms could be something worse than what I feel it is. Thanks!

(Both are eating and drinking fine. Lots of lettuce everyday, baby carrot the odd days, and I give them vet-prescribed Vitamin C tablets everyday.)