I've never heard of bristle worms attacking a live snail, but you never know.

There are worms called spaghetti worms that are long and skinny and bright red that do attack snails. But if you had these in great numbers, all of your snails would be gone, not just the turbo's.

Mexican Turbo snails are temperate water snails and do not live long if water temps are  > 77F.

However, they should live at least a few months even at higher temperatures. If they die within a few days of introduction and acclimation was done properly, I would suspect a predator, chemical factors, or starvation.

Predator- possibly a small rock/gorilla crab is in your tank. I had one of these in my tank for 2 years before it got large enough to cause havoc on my livestock. Red leg hermits are known to attack them.

Starvation- the larger turbo's eat a lot and can starve very quickly. IMHO, they seem to eat only certain types of film/macro algae and may not be getting the proper food.

Chemical- They slow down and don't move very much in low salinity (< 1.022). They also seem more active with iodine additions and higher alkalinity.