Guinea pig scratching a lot

[machuandpicchumummy]

Both my boys seem to be scratching themselves a lot more recently, they scratch with their back feet and also their teeth.
I checked their fur and can't see anything in there or any visible irritation on the skin. They look perfectly fine, not scabby. Vet checked Machu for mites a couple of weeks ago when he went to the vet for his sore ear and he was all clear.

Is this normal, could it be something to do with the hotter weather etc?

 

[Claire W]

The hotter weather could certainly be causing it but I would keep an eye on them and have them vet checked should they develop scabs / start losing fur / noticeable become uncomfortable