Dewetting in Sn Sufrace PCB in 2 Pass Reflow

Any advise about dewetting defect occurrence during 2nd pass reflow. Commonality on affected PCB having water marks near affected pad(s). Elemental composition found on affected pads without solder paste are Silicon and Sulfur. As well as in pad with Solder Paste. But if it has solder paste the Carbon content increase dramatically, not sure if it is just an effect of flux or increase is reaction of Sulfur or Silicon in Solder Paste. Your favorable response will be highly appreciated. Thank you.

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