While that doesn't look like a structural problem that would keep you from sailing, the tension in the shroud is the big suspect. You say you recently tuned the rigging. Was it slack before? If that cracked tabbing was put in place while the rig was slack and hence didn't put any strain on it, that may explain the issue. In any case, I am not familiar with the spray material you used there but I think you should glass it if you need flexibility compatible with your hull and deck.
1978 Gulfstar 50'
Clark Sailing Dinghy 10'