Hatchet fish not eating. Cory Cats making water dirty?

I got 6 hatchet fish (I think they are common hatchet fish even though
they were sold as silver hatchets). I have tried feeding them flakes,
frozen blood worms, and live black worms. But they don't seem to eat
anything. One problem is that there are other fish (tetras and
rainbows) that will come and eat the food.
But even when I have the other fish distracted and I drop some food
next the the hatchet fish, they don't seem to go after the food and the
other fish come and eat it.

Then I have 3 corys that seem to be very happy in the tank but then
they seem to disturb the plant detrius and make the water dirty. I
don't usually vacuum my planted tank but should I start doing it to
keep the water clean?

Thank you