Hi there

I have never seen different emulsions in the same box of paper, are you saying that you have balanced two different papers via the filters so that the two different papers match visually but with different enlarger settings, you then enlarge the image and make a test strip that matches , you then expose a larger sheet of the same paper and it comes out magenta.
If so , I agree with david and would first off start with more chemistry to attack the larger surface.
If you have tested the image at the larger magnification and used a smaller sheet and seen good results, then it is not the paper.
Please list the papers you are using and the enlarger settings with apeture and time and it may seem clearer