Do you have any photos you could share, as they might help people troubleshoot for you? And could you tell us what tip you used when piping the flowers in the photo?
In the absence of that info, my guesses are:
(1) You aren't using icing that's thick enough, and/or
(2) You're accidentally rotating the fat end of the tip upward when you pipe (rather than always having it facing down toward the flower nail).