Karen, have you received Phinehas's blood test results yet? Hopefully they'll be in the normal range. Here's a very good article about colitis that may be helpful to you: http://www.petplace.com/cats/colitis-in-cats/page1.aspx.

The part that might pertain to Phinehas is dietary change or stress or both of these. I know that you put out some fancy feast canned food for the kitten and it was out for quite a while before he ate it. I wonder of Phinehas ate any of this and maybe this upset his tummy since it was out for a while and he's not used to eating it.

I hope he'll recover quickly and that his appetite will come back. If he's bad about taking his liquid medication you might want to switch it to pill form. Some times the antibiotics can also cause diarrhea so you may want to try giving him some plain yogurt. Get well soon Phinehas.