I found these pee stains in my boys' cage this morning while cleaning. I've heard that the white powdery stains are caused from too much calcium. These stains are powdery, but not gritty and are kind of a light orange color. My boys are approx. 3 months and I think I've heard that young piggies urine can turn dark while drying. Is this what is happening? If it's a calcium issue, I need to investigate where it's coming from. They are on the KMS alfalfa pellets (since they are still young) and lately they've been getting green leaf lettuce, cilantro, peppers (yellow and green), a baby carrot here and there and some kale sporadically. Any ideas on what is going on in the picture below?