I have 2 18 month old females. They are bright and active. They seem just fine, not scratching or biting themselves. I use wood pellets as bedding and clean the cage thoroughly every week. In just the past few days both have developed dark red/brown irregular spots on their tails. The spots are not raised, just appear as discoloration under the skin. It looks almost like dried blood, but there are no wounds and, as I say, the color seems under the skin. I have done some "tail scrubbing", which I do every now and then to keep tails clean and healthy, and these spots don't come off. Anyone know what this might be?