Color of feces

[Leenknegt]

Hi all,

I've noticed the color of the feces of my gerbs is light brown instead of
dark or black. It is dry, but not very compact. I mix my own food, and
though all the animals are very healthy, there must be missing something in
their food. Could someone tell me what this might be?
The protein and fat is like it is suggested in the FAQ.
Thanks for any help!
Sarah