What is this?!

Please help. We just recieved this little guy about 3 weeks ago and this started happening 3 days ago. He was completely fine one night and the next morning it looks like he was sinking. His humidity is at 70% his hot side 88 cool 78 , uth and che on a thermostat I check Temps via gun daily. There's no chance these are burns. I don't have an Exotics vet in my city 

I should probably add this is a almost 4 month old Ball Python.

Hello!  I'm afraid that the short answer is that I don't know, but you can get some help. Luckily, there has never been a better time to assess online specialists in a full spectrum of fields, including reptiles, because so many vets are now consulting online.  The advantage of video consulting is that they can have a look at the pets' home conditions too, which are often extremely important when dealing with reptiles and have hitherto often been overlooked.  Your local / registered vet will have some basic competency in examining exotics so it's worth calling them;  if unable to help, they will know how and to whom to refer.  In the UK, owners do have a legal and moral duty to seek out adequate veterinary case for their pet, but so do vets to refer appropriately. Having said that, what could it be? I am afraid that this picture is unclear - I am looking at some brownish marks on the dorsum of a blurred central coil and have no basis to rule out burns. Although I hear that you have a thermostadt, the sensors often monitor one point in the tank and do not rule out overheating in other areas of the tank (snakes may seek out the warmest).  My understanding of heat guns are that they are not particularly reliable when assessing skin surface temperature, but please do speak to a snake specialist for that.     I also wonder whether UV burns may be a possibility, as these do not depend on the temperature? Good luck in accessing the help that you seek.  At the same time as contacting a vet, top quality housing specialists can sometimes be very interesting to talk to.  I would be interested to hear how you get on.

Ps has the snake lost weight recently?

The snake has not lost weight no. And the hottest part of the tank (uncovered substrate) is no more than 87 . I don't believe these to be burns but he has refused his second feed with me.  His scales are velvety to the touch even in the catered areas but his underbelly is weirdly squishy but not bulging. Exotics vet in my city isn't available until Tues at earliest if they will even see me and my regular vet fully admitted not knowing what this was. Someone mentioned blister disease but I haven't been able to find anything that looks like what's happening with him. He definitely isn't as active.

Me and your regular vet both!   But you know, there are many species and many different manifestations of disease in our job.  I would see it as a sign of strength in a vet to say 'I don't know what this is' rather than a weakness - in the old days, the old vets (and doctors!) used to bluff when they didn't know.  The dangers of the bluffing, hero-status practitioner have being recognised and we vets are much more likely to 'admit' when we do not know what is going on.  This is a good thing. As a professor once explained to me, the art of medicine is not in recognising everything first time, but in knowing a) how to find out what it is, b) recognizing how urgent it is to find out and c) working out what needs to happen in the meantime (e.g. pain relief, antibiotics, fluids etc. where applicable). I don't know if that helps at all.  I suppose the next question for your vet is how satisfied they are with a) b) and c) - does this referral have to be made faster, for example, even if it has to go further afield, or will it wait?   If it needs to be made faster, who are the other exotic vets who can speak to them?  (they may not have to be in the same City - I have taken second opinions from another country before). I would be truely fascinated to find out how this case ends.  Best of luck.