I was just going through some of the previous galas and realized that Udit Narayan praised Amit only twice whereas he always find ways to praise Prashant.
So I have two theories
1. (Don't pelt me for this) Udit ji is worried about NE votes getting distributed between Amit and Prashant. With Amit out of the contest Prashant would stand a chance to win that way which will make Udit ji happy for obvious reasons😉. Aakhir ek hi matrabhasha bolne par thoda to pyaar aata hai na😛.
2. Udit ji thinks Amit is one of the best so he wants Amit to be perfect always. Being the hardworking one that Amit is he would take the criticism in its stride. So he is being critical.