OP, dont keep questioning it. Apologise if it makes you feel better.
I don't get the POV of posters who are telling you, you are wrong, as I do treat my adult children and their partners differently, the difference is my son and daughters partners don't care about things like that so I have never had that problem.
Also partners have parents who they love and they will treat them differently to me. Honestly, I really do not care.
If OP apologises to keep the peace, that's OK as well. This will blow over.