Was your developer stored in an oxygen-free (i.e. glass or PETE bottle under butane or with air removed) and in the fridge? If not, it was probably dead. Stored properly, it should have been fine - I've tested 4 months and found no change, but it will die in a few days if left with oxygen.
An "odd" colour to the dev implies that maybe you put bleach in instead, or maybe you accidentally dumped some blix into your developer on the previous session. It also goes a bit darker from oxidation but it's harder to tell the difference between tea-colouring from oxidation and tea-colouring due to running a bunch of rolls through it and having some of the sensitisation dyes wash out.