My baby cal king went into shed about a week and a half ago and he cleared up around two days ago. He hasn't shed yet but I haven't fed him since he went into blue so I offered a pinkie and he took it. About a hour after I found some smelly, sticky dark brown/red stuff on his substrate (I included a photo). I don't think it's the regurgitated pinkie since there's no mouse but it's too little to be poop either. Also he dragged the pinkie into the tunnels he made (aspen shaving substrate) and maybe swallowed some if that could've caused it. I've fed him two meals so far and haven't had this problem. If it helps, the humidity in his tank is at around 47 percent (I use a digital hygrometer) and his hotspot is around 85-89 degrees. Please, any help is appreciated!

https://imgur.com/a/ZMjvuX2