I believe fellow TAs are giving students answers and inflating their tutorial average, what should I do? I am first-year graduate student doing teaching assistance for an introductory calculus course.

The course is taught by four instructors, with 12 teaching assistants in total and I am one of them.

Each instructor has three assistant underneath him or her and I am associated with one of the instructors along with two other TAs.

At the end of each hour long tutorial, the TAs will conduct a 20 minute mini-test. Each test has two computational questions selected by the professor. The test questions are related to the lectures prior to the test, and the time prior to the test is for the TAs to review concepts in the lectures and do some examples and exercises from the book. The exercises are drawn from the same source as the test questions, but they are obviously not supposed to overlap in any way. 

I don't have strong evidence, but I believe that the other two TAs (who have been  doing this course for longer than me) are giving the student answers, and their students are outperforming those students in my section because of it. 

What aroused my suspicion was when I graded the tests from their tutorials. We grade these tests on a rotation. There have been 9 tests so far, so at this point I have graded three of the tests. 

What I found is that the students of their sections will give perfect, textbook solution like answers. All the students would make the exact same assumptions, almost as if all 30-40 students are copying from one another. In my section, the students struggle with their questions, sometimes not finishing them. When they do provide answers, there is a large variety of responses as expected of a calculus course. Therefore the students in my section have lower averages.

I don't believe that they are giving students answers directly. Some students would have sounded the alarm by now. What I suspect to have happened is that these TAs are doing the test questions during the tutorial and mixing them into the reviews. This would explain why so many students would follow the exact same procedure, yet still making some mistakes. 

I wonder if these TAs are gaming the system. The system being the TA reviews at the end of the semester. These reviews are internal and are used to promote or select future TAs. I also feel bad for the students in my section. I feel that they are being cheated by the people who are supposed to instruct them. 

I don't have firm evidence, but I fear that the professor is also in on it. When I first observed this large disparity between student performance, I mentioned to the professor. But there was no reply. Therefore I am afraid of talking to her about this. I am new to the school therefore I don't have anyone I can trust.

What should I do in this case?
Is it possible that the other TAs, by having done the course before, have a better overview of the kind of questions asked in the exam (based on those of previous years), and therefore are better able to train students for those exams? That would explain the facts as well, without anybody consciously in the wrong (and it is always worth to explore such possibilities).

I can also understand that your professor is not actively doing anything about it as long as the difference is not too big. Some TAs are better than others, some groups are better than others, there is always noise and some differences between groups are to be expected. I was a TA for several math courses where we would grade weekly assignments of our own groups (that counted for 10% of the final grade, next to a 90% final exam). I would grade harsher than other TAs and my group's average of the homework would be lower than that of other groups. However, my group tended to do better at the final exam, I believe in part because they were pushed harder to make an effort. What I mean to say is that worse intermediate test results don't say everything.

Unless you have hard evidence that your fellow TAs are 'gaming the system' I would be hesitant to attach too much meaning to the present facts. If, besides this, their manners are unpleasant or the group atmosphere isn't right, the easiest solution would definitely be to avoid them by not TAing the same course next year.