With film fixer, it is very common to see some tint from the dyes that are removed from the film, especially from t-max. This coloration is harmless and generally fades away within 24 hours or so. With prints, some papers can also leave some color behind in the tray. If your fixer has become yellow, it has likely been used too much.
This tint could also be carry over from the stop bath tray. If enough prints are placed directly in the fix from the stop bath, without allowing some time for the print to drain first, you can get enough stop bath in the tray to add a tint. It is best to drain prints until the point of separate drops.