Hi Vega: Just a few more thoughts.
How old or what's the weight of your ball python? If it's a baby, it should go through a shed cycle every month and what you are describing as an overall dark tint sounds like just that to me.
If it isn't a baby:
1. Check out the bag of Aspen and see if you have an ingredient list (should say 100% aspen, if it doesn't I would toss the bag assuming that it's a mix that belongs into the hamster department).
2. Where are you taking the temps? Bottom of tub over UTH, bottom over the bedding, mid height ...?
3. Here's a couple pics of a burn that led to a dermatitis (dermatitis can have many different causes). This snake was exposed to too much belly heat and developed a mild case of dermatitis (scale rot). Pics aren't enhanced in any way, so it should give you a good idea of what you don't want to see on your ball python.

Prior to shed cycle:


During shed cycle:


I'm pretty sure your BP is just simply getting ready to shed and in another 24 to 48 hours from now you'll notice the cloudy eyes.