Hi Prathyusha, hope you are doing well, yes you can send one more application for mtech for iit madras. You can not edit the application but you can re-apply for one more application by paying the application fee. If you want to apply for more than one application, you are surely allowed to do the only condition is you need to pay the application fee for all the applications you applied. 

I think it helps you!!!

Keep Smiling:)

Wish you good luck!:)