Independant convection oils of each pass is the best configuration for OLS.However it is a little costlier. Though this is not a must for good OLS. Trick is to lower the adjacent pass COT also while doing OLS.
Convection temp going high while injecting water is not heard of. Is it due to less than required water/steam injection in pass under OLS?
Excess air in the specific pass does help to lower the temp during spalling.