Not enough information provided to be able to answer. How a big a pot, how many seeds, what kind of potting medium, how was it watered.....only rain water?

Improper soil moisture (not always easy to judge from the surface) is the most likely cause. Keep a closer eye (or finger) out for moisture levels.

But as GG suggested, it's hard to know for sure without more info (or being there in person).

I was going to grow these in the next day or two myself. Suggestions for potting medium??

alaMel,

There are as many answers to that as there are answerers. Even variables like your climate and how often you plan to water will play a part in determining which mixes would work best. I'd recommend doing some reading over at the Container Gardening forum. Al's mixes may be a little overboard for growing Morning Glories, but the thread is just packed with useful info that can help you make better decisions on potting mediums (see link below).

Here is a link that might be useful: Container Soils - Water Movement & Retention