Hello. How long has this been going on?
Has there been any change in the color of the droppings?
You are positive it's his droppings that have changed and not hers?
I see you changed food. What did you change from and what are you giving them now?
Do you put any kind of additives in their drinking water?
How long have you had them and is one a more recent addition than the other?
How long have they caged together?
The extra information will help me give you my best advice.
Thanks, Patricia

