Thank you very much for the suggestions. I shall try DE. I looked at every square cm of the plant, I am not able to see any caterpillar with my bare eyes, but it seems like the most likely culprit.
I have a herb planter in the kitchen which currently has mint. There seems to be some pest that comes in only at night and eats the leaves. The result is holes in and browning of leaves. I have attached pictures here. There are also black specks/dots which indicate feaces. I am not sure what critter / insect this could be and what remedy I could use. Would anyone be able to help?