What could this be?

[Briser]

Okay so, upon closer inspection and cleaning with a cotton swab, it doesn't look like caked on poo at all? I searched around the net and found a picture that is as close as I could find to what their bums look like. Here it is:

Is this normal?

[kyrilliondaemon]

Yup completely normal
Genitals and scent glands can naturally become pigmented in hamsters, our syrians genitals have more pigment than that now and its perfectly normal

[Briser]

Okay, thank goodness! It definitely wasn't that dark the other day, so I'm curious as to how they both got so dark so fast? I give them a good checkover every time I clean their cage and I was so shocked to see the darkness that I was almost positive it was caked on poo!

[kyrilliondaemon]

Er... I have no idea to tell the truth lol
I think Scamp developed it quickly but both of yours developing it at once is possibly unusual.

[jewelkrist]

It is ok they are developing there is no worry about them.
but now take proper care you should clean there area and to feed them portion food by which they will have the proper digestive system.