Soapy you say. Flavors can be hard to communicate. Until I brewed a beer with tons of diacetyl, and had it pointed out to me, I didn't know for sure what it tasted like.
The thing common to all your beers is a high fermentation temperature. At first in both primary and secondary, later just secondary. Various esters are produced at elevated temperatures, but mainly in the first few days. I don't know what may be happening with the beers where the primary was at a low temperature and the secondary was at an elevated temperature, but I wouldn't rule out the increased temperature as the cause. As others have said, I'd definitely forgo the secondary and hold it in primary for four weeks at the cooler temperature and see if that makes a difference.
If you are a member of a club take a bottle or two to the next meeting and ask some of the sages what the off flavor is. They may perceive it differently than you do and would be in a better position to give you feedback.
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