That's your problem, they can easily get over 54 degrees when unregulated. Your BP very likely has been burned by the heat pad. You need to get a thermostat as soon as possible.
Where do you live?
Here are 2 good ones but they aren't avaliable everywhere.
If you can't get a thermostat, then you should just get a heat lamp. An infrared heat bulb is much safer. The only issue with them is they reduce the humidity in the cage.
Unregulated heat mats can get hot enough to kill a BP and in rare cases start a fire.
I'm not sure if these are scalable to you but I have had good luck whith these bulbs:
That's your problem, they can easily get over 54 degrees when unregulated. Your BP very likely has been burned by the heat pad. You need to get a thermostat as soon as possible.
Where do you live?
Here are 2 good ones but they aren't avaliable everywhere.
Not that I'm one of the more experts on here, but when Quetzal's heating pad malfuctioned he had very similar symptoms accompanying his burns. You're going to want to get the uth under control asap but also get the closest thing you can get to betadine and use it to treat the brown stuff. I used neosporin and made the unpleasent discovery that neo makes scale caps come off. The shed should help a bit as well; it only took one for Quetzal's belly to be back to normal but I jumped on it right away. Make sure you keep the enclosure clean to keep infection from settling in. Within a few weeks to a month or so, should be good as new. Just make sure your uth is controlled or you use heat lamps on a dimmer if you can't get a thermostat and that your humidity is spot on and she'll heal up nicely.