Was the car on an incline when you noticed the leak?
I would locate where the antifreeze is dripping and visually follow the trail until you locate the source.
I have had antifreeze leaks which made its way down the car frame.
A tail pipe repair should not cause an antifreeze leak.
1998 Mercedes E320, 200K Miles
2001 Acura 3.2TL, 178K Miles
1992 Chevy Astro, 205K Miles