bald spot

Hey, i first thought it was just dry skin however there are now clumps of hair coming out and bald patchs any idea on what the issue is and how to treat

I recently gave one of my guinea pigs a bath and realised he has a huge bald patch behind his ear? His other ear doesn’t have this. I’ve also noticed black little specs, I’m not sure what they are and if the bald patch is normal

Hi- I am new to this fourm and I hope you all can help me. This morning I noticed my pig had lost a patch of hair just above her right front foot (not too big but noticeable). I have also noticed she has been itching (or gnawing, she I guess chews on it then pulls, my previous pigs did the same...