Balance/movement issues?!

[Invisible Snake]

Has Buck been drinking water? I think I also read that dehydration may cause seizures, I'm not 100% sure though.

[Greg'sGarters]

Try to notice if he drinks the water, that could also be a problem if he isn't drinking.

[Buck]

Now that you mention it, I haven't noticed her being at her water bowl much... No swimming or drinking. I just pryed her mouth open and dropped a little bit of water in. Should I keep doing this, or could that stress her out? What are the best ways to rehydrate a snake? This seems now to be the most likely explanation, although I'm not sure why she hasn't been drinking....

[Invisible Snake]

No, whenever you pry open a snakes mouth it's very stressful for them. Just place her in a small escape proof critter keeper with shallow room temp water and let her swim/soak in it for like 5-10 minutes.

[Light of Dae]

What kind of water? is there a chance of salt in the water? Dehydration or something in the brain...

[snake man]

Did you talk to the vet yet?

[d_virginiana]

Yes dehydration can cause seizures, but if clean water is available a healthy snake will not just refuse to drink for extended periods. If a snake with available water becomes that dehydrated then the dehydration is most likely another symptom rather than the cause of the problem.
What have you been treating your water with? Doubt it will help, but you can try buying a gallon of spring water and using that instead just in case there is something odd in your water.

Just based on what you were saying, it sounds neurological. Sometimes neurological problems like this can be caused by a vitamin deficiency; usually because of the wrong diet. Doesn't sound like this is the problem since guppies are an okay food, but it's worth mentioning. Sometimes a vitamin injection you can get from the vet will fix this problem. Sometimes the damage is too much.

How old is the snake? Sometimes genetic neurological problems don't show up until they get older. IMO this is probably what it is. Like was already said, by the time anything starts causing seizures like that the chances the snake will survive are pretty low.

[Buck]

I don't treat my water, as where I live the water is so clean that there is absolutely no chlorine in it at all. She's just 10 inches in length, so not that old. The vet said that he could not find any mites, but he did find that Buck had tense muscles around his jaw area, making opening and closing the mouth difficult. He did conclude that it was likely dehydration, and proceeded to gently massage her chin, stimulating mouth opening. He gave me a syringe to place a water droplet in her mouth every fifteen minutes. He told me to come back in to the clinic in 3 days for a follow-up. I'm still open to suggestions, as the vet and I are still somewhat confused. I will continue to update as things progress, thank you!

[Greg'sGarters]

Check for mouth rot that might cause the tense jaw feeling.

This Is A Picture Of A Boa With Stomatitis (Mouth Rot)

[guidofatherof5]

I find the tense jaw muscle thing rather strange. Tense compared to what?