For the record, they do take into account vegetarians. In the article it said that any prisoner could have a vegetarian diet, by making a formal request and some paperwork with the prison chaplain. The detail, of course, was that not knowing English, he did not had the language abilities to do that.
Regardless, as Jcat said: There is virtually no way that prison staff could not have noted that there was something wrong. Find an interpreter and get him to medical attention. Any other behaviour is short of murder, as they were virtually letting him die while knowing what was happening from all the complaints of other prisoners.
In ANY courtroom in most of the world, any defendant or witness who does not speak the language of that place has the right to an interpreter. In California they even put it on the state constitution. But, in a situation where otherwise someone will die, the prison would not find a interpreter, much less get him medical help.