Can you be more specific? Which part is more liquid - the white urates, the brown fecal, both? Any change in color or smell? If it's only the white urates that are runny-ish, then yeah, it's likely from the silks because they do a great job of mega hydrating. She's just ridding herself of extra water she doesn't need, reflected in the urates. That's assuming there aren't any other problems as you said.