I thought DKS, as well. I so wish I could post the video I took of him.... and I don't use ANY aerated chemicals in my house, especially not around my Ts. Perfume I use ONLY in my bathroom upstairs, whereas the tarantulas are downstairs. I use organic cleaning agents, no chemicals in my cats, no carpet powder or air spray. I wish it was something so easy to pinpoint. the vermiculite mix that he's on, he's been on for a while now, and I have had crickets live on it for a hot, also. (I have a tank where I keep bought crickets to gut load). I usually feed them dubias that I breed myself, feeding a diet of fresh fruits and veggies, and never using any chemicals near them, either. It just looks like he is in an immense amount of pain, and I can only compare what he looks like to a human trying to rip their skin off. It is heartbreaking to watch him. I'm going to try and upload the video.generally, spazzing out and having heavy difficulty moving is DKS. or tarantula poisoning. only way this can be avoided to to not use chemicals around spiders, like at all. this is almost always fatal. i have had one survivor however, a N incei sling that molted out of it after surviving for weeks with it.
poisoning can happen from many different chemicals. think of which you have used in your tarantula room. perfume, air freshener, flea spray (?), insect repellant, etc.
what brand of vermiculite did you use? a good way to test for anything bad is to leave a few crickets in a container of it for a couple days. if the crickets dont die, its most likely safe.