I highly suspect that the average temp of the wort in the fermenter was considerably higher than the 52 F indicated on the fermometer strip. The ice water batch would cool the wort slowly from the outside inward. The fermometer attached to the outside of the better bottle would only be reading the wort close to the side of the bottle and where the wort would be cooler. Adding to the problem is the heat that is generated by the yeast especially when they are fermenting at a high rate. This will slow the cooling down even more. It can take quite a while to get down from boiling to 52 F. I can get close with my counterflow chiller in the winter, but still need to refrigerate the fermenter for a few hours to get it to pitching temperature. Did you aerate the wort well? If so, that should have mixed up the wort pretty well and you should have gotten a reasonably accurate temp measurement at that point.
I'm just guessing on this and could be completely wrong. Just some things to think about.