Vinit does tend to sing nasal, but that is a compensation mechanism when they cannot sing highnotes. When you get classical training, my guru would repeatedly stress this fact and try to reduce it. So as I have said before, he needs to get lots of training to sustain his voice, sing full throated without sounding like yelling and have good breath control.
I dont think Debojit does nasal, but unfortunately he cannot sing high notes and I think he is smart to change subtly when the notes get higher
If you watch Feb 3 video where all the three sing with a harmonium for Ghai, you can clearly see the real voices and what I am talking about. You have to hear their voices without music to understand that.
Hemachandra and Nihira are the only singers with excellent tonal quality, pitch and breath control and have complete control on high notes.