It began with tingling and numbness in the graduate student’s fingertips and weakness in his legs. As summer ended, it got worse, as the numbness spread across his left arm and all his fingertips.But after weeks and visits to the University of Wyoming student health clinic, he told investigators he couldn’t figure out what was wrong, court documents show. He had mentioned to professors and other researchers that the hot water he regularly drank in his office tasted off, two professors told CNN.Then, he found a white substance near his coffee pot and water bottle, according to a chemist at…