I known it might be hard to find out but it could be the way the razor was honed.

For me when I shave off of a coticule or other natural stones I get no irritation. But if I get a blade that has been sharpened with a norton or other synthetic hones they irritate me to no end.

I know skme other members here have mentioned the same so that could possibility.

But most likely it is just you gotten used to a new blade.