If you are using a leaf tip like 67 or 68 have you made sure that you have opened the tip wide enough the first time you used it.? I use my spatula to open the tip. Are you putting piping gel in your thin icing? Piping gel will help you to pull your icing to a point upon completion of your leaf..
You can either push those two split ends together to form a tip (use your fingers), or you can use a tip # 352. That is my favorite leaf tip anyway. I also have trouble using the tip that you are talking about.
Try the new tip I am telling you about and it will change yourflowers forever!
FAITH sees the invisible, believes the incredible, receives the impossible!