It does look like pest problem. That was what I initially suspect.
I check it every night. There is no trace of worm/caterpillar/snail/slug. They usually produce droppings or slime nearby as pointed out by many. Grasshoppers are not too picky when eating. Old leaves are as tasty as new one for them. A note is that, another amp next to it is fine. So, I kind of rule out pest problem.
Dead tissues start appearing on new shoot. It does not look chewed but appear burnt. As the leaf expands, dead spots fail to form leaf.
After some thoughts, could it be overfed? I feed it frozen bloodworms. A few worms once a week in one pitcher. Every leaf is progressively bigger. The other amp has small pitchers. So, no feeding. That seems to be the only different. Yes, I know amp is supposed to be vegetarian...
I am not sure if anyone feed/fertilize amp has plant matching this symptom?
I'll stop feeding and continue to look for pests. Thanks.