Out of wet food usually give can

So we have gone through stinky poop and cough and sore red throat and a single cell organism with our kitties and they have just finished up medication which seems to have done their job. I was first told may be it was the food cause of soft stinky poop. So we changed and have stuck to one kind. Do you think if they found the organism in the poop it was probably not food related? I ask cause I am out of the soft food I was giving them from the vets and they are not open tomorrow and I can't get their until Monday evening. So I have some wellness and blue buffalo cans for kittens which we thought may was the problem. Would it be okay to try them again? I would like to get them off the vet food but don't want to stress them out too much with switching, thoughts ?

what you're describing sounds very much like what we had with Matt when we got him-they tested for single celled organism called giardia(spelling may not be correct) 

your symptoms could be from the organism(likely), or they could be from the food, but it shouldn't hurt to feed them for a day on what you have until you can talk to the vet.