Funnily enough after some successful reversal processing I started getting yellowy/brown images since reading this thread. This was occurred both with second exposure and development and with chemical reversal. At first I thought it was the bleach and/or clear as it was getting a bit old but on renewing that, same result. This pointed to the first developer, I use Suprol, and the bottle had been open for quite a while. With fresh developer, the tint went away. But, what is interesting is that with slightly oxidised first developer I was even getting the stain with chemical reversal (using "Iron Out", not using that developer.

Thanks, for the tip on the ferricyanide bleach/fix, johnie, I wasn't clear on the recipe 'pure hypo 1:1' seems a low dilution , i.e. strong concentration of hypo, but I added the ferricynaide to my usual solution of hypo and it did brightened up the images on the the strips I tried.