No, it's a weird one. Generally I only run Geoff's, but I have occasionally picked up a bottle of some generic Blasters or similar if I've run out on the day. Honestly no idea how long that's been in there. Although now I look at it I'm wondering if the bb at the bottom of the loader is a bit oversized too...
I guess the answer to this is to shoot more ammo so it's not sitting around as long? Airsoft solutions to Airsoft problems.