How about a pull process?
Expose at 50 Asa and pull for one aperture / shorten FD time for 2 minutes.
Be aware, not all Films like to be pulled, the “late AGFA RSX II 100” for example was pretty perfect in color balance, just a bit softer, but most films will show some color deviations.
Because your film is already shifted to magenta, only a test will show if any usable slides will occur after pulling…
If you do have enough chemistry to play around a bit, try to increase the pH of the color developer with small amounts of NaOH or KOH 10% solution. Maybe 2-3ml / liter for a first test. If you desperately insist in using the films a complete homebrew would be a possibility, decrease Sulphite and KSCN a bit in the FD, doing still a pull process. Decrease the Citrazinic acid in the CD and adopt it’s pH till the color balance is better. But it may be questionable if it's worth the trouble…
Regards Stefan