It could be that:<br />
a) You are ill<br />
b) You are stressed<br />
c) The food was not as fresh as it could have been - supermarkets sometimes do date wrongly.<br />
d) You are taking medication??
the food you ate may have had some preservatives in it that are disagreeing with you now.
depending on what you ate, it could; its only if your stool was tan or without color that it would signify trouble.