Kitten has weird dark green poos - please tell me what to do

I'm actually starting to get a little worried. My 12 week old kitten has been eating Natural Choice wet kitten food (various flavors) a few times a day and Wellness Kitten Health dry kibble is left out for him, though he doesn't eat much of it. His poos are black/green and slimy ALSO, my goodness he is stinky. I think he is having gas problems as well as a nasty smelling litter box. Can you help me, ideas or suggestions? Not sure if I should switch foods right away or to what food I would switch?
Thank you!

You need to take him to your Vet. Black stools often indicate blood in the intestinal tract.
Get him checked out with a clean bill of health before switching his food.

Originally Posted by Kai Bengals

You need to take him to your Vet. Black stools often indicate blood in the intestinal tract.
Get him checked out with a clean bill of health before switching his food.

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100 % agree with the above... the issues may have nothing to do with food but Only a Vet can tell you what is going on