Animal Welfare Professionals

Hey all I'm new to this site. But was hoping someone may be able to give me some advice. I just adopted a second cat so my first 7mounth old cat has a friend to play with. Well I had a second liter box set up and it hasn't been used since day 1 when I kept them separated. I assume they are now using the same one cause I haven't found any poop or anything else where. How can I be sure? Also they seem to be sharing food as well I got a second food bowl and such should I keep feeding them seperatly and hoping they both eat enough even if they eat out of both bowls? Ive only had the second cat for 5 days. Lastly sorry one more question. I'm taking one to the vet tomorrow and they asked for a stool sample any suggestions on how to know which is which poop besides just stalking them to the bathroom? Thanks! Hope this is the right place for these questions sorry if not 

I would put the 2 bowls side-by-side and let them share as they want to. The 2nd litterbox may be redundant, but you never know when they will change their minds and start using it. If they don't use it at all, I would just empty it, put it away and save it for when you need a stool sample. When I have to get a stool sample, i usually set up a bathroom with a bed, food, water and a litter box and close the cat up for the night alone...that way anything in the box could only be that cat's...er...contribution. good luck!