I don't think ur leech line being too tight would do that (but to be sure, check for sail distortion along the wingtip/trailing edge).
It could also be from too many repeatitive yoyo wraps.
Once you get those patched, try re-enforcing the trailing edge with black duct tape. Take a roll, and cut it down the center (essentially cutting the width in half), and wrap some along your trailing edge, extending 6 inches to either side of your standoffs. Also put some tape just above your yoyo stoppers. When the tape wears out, just peel it off, then replace it. Beats replacing a T.E. or L.E.
Hope that helps m8.