There was no reference cited for the supposed first marriage of Rachel Wynn to Edward Trowbridge.I checked the 1860 and 1850 census for Rachel and found her as Wynn in both years.In fact there were no Trowbridge families near the Wynns in either census year.So put the first marriage in the skeptical column for now.
1860 OH, Washington Co, Watertown
WYNN Joseph, 72, PA Rachel, 23, PA Margaret, 32 [sic], PA
1850 PA, Beaver Co, Raccoon Twp
WYNN Joseph, 62, farmer Sarah, 52 Joseph, 22, farmer Margaret, 29 [sic] Susanna, 27 Rachel, 17 [sic] Amos, 15 Sarah, 13 all born PA
As to whether Rachel and David Piatt died on the same day, I would be skeptical of that, too, until proof is found.It's not impossible.In other research I've found two times when the father tried to boost the stove by throwing kerosene on it with horrific consequences.But mistakes can be made in copying information, too.
I believe death records should be available for that time period.You might inquire of the courthouse.If the dates turn out to be the same, certainly there would have been something in the newspaper about it.