Did you...turn on the lights?
After the B&W dev and wash (which was carried out in complete darkness naturally) , yes. I'm trying to think why this would matter though
Initially I'd put it through the B&W dev for a reversal process. The first sheet I did appeared way underexposed, and it had been shot a stop faster than this one, so I decided to see if I could just bleach it and then re-develop the B&W image with the RA4 developer and get a colour neg out of it.
Should the process not have gone something like ...
Darkness
1. B&W dev (and wash)
Turn on lights (this exposes all the undeveloped halides, but they'll be removed by the fix)
2. C-41 fix (removes all the exposed but undeveloped halides)
3. C-41 bleach (converts exposed and developed silver back into halides)
4. RA4 dev (re-develops the halides and in the process activates the colour couplers, producing a colour negative image)
5. Bleach and fix again to leave only the dye layers.
Or at least that was the theory