yellowing of paper?

In some of my prints I've noticed a slight yellow tinge to the paper, others are nice and bright white, often I dont notice unless they are side by side. I'm sure its something simple, but I'm new to film. The paper is illford RC multigrade, not sure on the developer as I havent heard back from the prof. yet to find out whats in the tank.

Let's start with the basics..Did you correctly fix the print, agitating it intermittently, for the recommended time?

yup, correctly according to the professor, again I'm waiting to here back from him on what chem so I can find out if I've got the times. Fixer could be old, however, I think that this would reflect in all prints from the same bath, its not weakening because I got white prints after yellow prints last night.

Ishotharold said:

yup, correctly according to the professor, again I'm waiting to here back from him on what chem so I can find out if I've got the times. Fixer could be old, however, I think that this would reflect in all prints from the same bath, its not weakening because I got white prints after yellow prints last night.

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If you are working in a school darkroom, you probably are a victim of poor quality control of the fixer, hypoclearing bath and inadequate washing. School darkrooms are notorious for poor quality standards.

Incomplete fixing, caused by either exhausted or old fixer, insufficient fixing time or poor agitation, is detectable by sulfide toning. Apply a drop of working-strength sulfide toner to an unexposed, undeveloped, fixed, fully washed and still damp, test strip for 4 minutes. The toner reacts with silver halides left behind by poor fixing and creates brown silver sulfide. Any stain in excess of a barely-visible pale cream indicates the presence of unwanted silver, and consequently, incomplete fixing. Compare the test stain with a well-fixed material reference sample for a more objective judgement.