If the above still doesn't solve the problem, consider headstay sag
relative to rig tune or adjustment of halyard tension/jib cunningham
(most J/24s have them). A good way to test would be to set the genoa
without the main and see if you can get all the tell tails to stream.
Fractional rig one-designs like J/24 used to all use max headstay, but
current tuning concepts tend to favor significant adjustment for
headstay sag.