need help ,Switch major

[justvisitor]

Hi guys, I am an international student and taking Master's program in Chemical Engineering in the USA. I was lucky, got a scholarship from the US govt and My Univ. My school ranking is between 100-125 based on usnews.com. I had done 2 semesters while having a terrible health issue. I got one B for Fossil Fuel and Renewable Energy, one B- for Heat Transfer and three C for other courses. The problem is with 3 grades below B- usually, there might be a termination. I am so scary now. I decide to switch to Material Science . I need strong argument/ reason  to fill the form of department change, do you guys have any idea of what I should write in the form?