Not only do snakes not need UVA OR UVB, torts, monitors, geckos, chams, etc etc etc do not need it. At least not those stupid bulbs.
Ok, to clear that up, they do not need special bulbs or the sun.
Lets start with snakes and I will not use others experiences(heresay), I will do what this forum SHOULD be about, I will use my firsthand experience.
I have kept and bred kingsnakes since 1964, continuiously. Generation after generation after generation. Inbred, outbred, created morphs and phases, and developed lines. Which is not bragging in this case, its to show that all manner of breeding was done. Which means all manner of genetics was explored.
And during all these decades and all these different species and genetics, I never had a need for a single UVA or UVB bulb.
During this time, we supported snakes to grow to full size and record size. We supported snakes to reproduce under a year of age and still grow to full or record size. We supported snakes to live up to thirtyfive years. We supported females to multiclutch for an average of 15 years, then single clutch years after that.
Now for the kicker, all without UV bulbs and in a good percentage of the case, any lite bulb what so ever. Heat was offered via heat pads and strips. And there never was problems your experiencing, or any other base health problems.
What you have is a base health problem that is caused by a compromised immune system. Such things as mouthrot, common infections, Upper respitory infections, are caused my common gram negative bacteria. These are NORMALLY controlled by a normal immune system. Of course there are more types of pathogens effected by a compromised immune system.
Oh by the way, I work with snakes in the field with longterm field studies and have spent my long life in the field over much of the world. Wild snakes(reptiles) use a range of temps to accomplish a range of physical goals.
Simply put, they have a temperature area to rest and conserve energy(what reptiles do) they have a temp area to digest prey, and a different one for each size of prey. They have a temp area for shedding, and a temp area for incubating ovum in their bodies, and for embryos in their body(species dependant) I can keep going but lets get to the point, they HAVE A SPECIFIC HEAT RANGE(efficiently) TO BUILD AND MAINTAIN THEIR IMMUNE SYSTEM.
Now for your answer, when snakes are brought or kept(cb) in captivity, they are often not allowed to reach the temps THEY WANT, they are often kept in temp zones above or below what they NEED. This does not allow that snake to function in a natural way. So it becomes both mentally and physically STRESSED.
This STRESS causes the immune system to weaken and eventually fail(compromised immune system). Then our captives fail from the most common of disease vectors.
That your VET blames bulbs(uv) and does not understand the immune system, is cause for you to find one that does. Get rid of your vet and find a good one.(nothing against your vet personally, but consider there are good and bad individuals in all trades) what you have done is succeeded in finding a bad one.
Now back to your snake, you mention some goofy bark. Can such things as poor substrate choices cause such things are your experiencing, yes to a point. Some substrates are prone to bacteria build up, and that coupled with a compromised immune system is a sure path for a sick or dead snake. Some substrates are uncomfortable, and that causes physical stress.
Now lets talk about you, which is something the vet should have done. You sound like a very very newbie keeper. Yet, you picked the cage and its contents and its conditions. You picked them for your needs under your understanding. Your not being a bad person, your just doing what you think you know.
What you should have done is, set the snake up in PROVEN methods that allow the snake to be healthy and progress to a normal life(as normal as can be in captivity)(which is not all that normal) Even if you think its ugly. Your task is to first maintain a healthy snake. Then suit your visual needs.
Once you have a normal growing healthy snake, then you can decorate the cage to something that you like. Then if the snake ceases to be healthy, YOU KNOW YOU DID SOMETHING WRONG. In nearly all cases, we keepers are the one doing something wrong.
The horrible thing for us keepers is, snakes are a genus, they are a species, they are a subspecies, and often they are a morph. But more importantly, they without question are individuals. As all humans are humans, we too are individuals and have our very own set of needs. This is so with snakes, they ARE NOT WINDUP TOYS.(many here treat them as such)
So your individual snake may REQUIRE, the ability to be secure(hide totally) And hide in proper conditions, not too hot or too cold or too dry or too wet. And have the feel that individual requires.
The truth is, strong individual snakes can indeed get by with average conditions(common on this board) but weak or compromised individuals cannot, they suffer from average conditions. That you just acquired a snake, most likely means it was subjected to conditions that test its strenght, you know, petshops, shipping, moving from home to home, moving from nature to captivity, etc. So your individual may be compromised already.
So please go find a good vet and go tell that other vet off.(show this post) And I wish you luck with your wonderful kingsnake. Cheers