Confessions of a Cat Breeder

Dear Jasmine, I'm new to your site and I need some help. I fostercare cats and kittens for a rescue group. The 7 kittens I have right now have had diarrhea since I received them at 3 weeks old. The stool sample was negative for parasites. I found round worm in the stool and wormed them for round worm. I'm just so frustrated with the diarrhea. I am giving them Imodium AD for it. The Kaolin Pectin didn't work. I was feeding them more KP than food! They were on a soft/kibble diet and I am recently trying straight kibble. Prior to that I was boiling Chicken and feeding them that with Pumpkin. That worked good for fattening them up and getting them over the dehydration but now I can't get them on a regular diet and they are due to be adopted already! They are 9 weeks old. Biscuit, Tater Bug, Kelly, KC, Cheeto, Lucy and Blu. I love cats but these have really worn me down. I have a vet appt. scheduled for them but I thought maybe you had some ideas?
Thank you for any help or suggestions.