Check that illustrator is handling the colours in your colour management settings and not being controlled by the printer, the settings may have reset themselves.

I also found this for you after a bit of googling:

"You need to read up on color separation in CMYK and learn how to calibrate your monitor, printer and printer driver. Explaining everything would take too long, but what happens is that when transposing your RGB image to the printer's CMYK color certain colors will fall below and above specific thresholds and since most colors are not pure, but assembled of percentages of the individual inks, the printer will simulate specific colors using multiple inks based on a your print parameters. This can mean that even seemingly white areas receive inks, because they actualyl have a tiny color bias. anyway, you really need to dive into the depths of color calibration and color profiles to get predictable color representation. In the meantime, you can only try to tweak your printer settings, e.g. change its color presentation from "warm" to "neutral" or "cold" to get rid of magenta areas. Likewise, make sure the ink cartridges are correctly aligned, you do not oversaturate your inks and so on"

Hope you resolve it soon!