I don't think bleach part goes bad. I'm using the same one for over a year now. It concerns me that your bleach lost activity though...

I noticed, the re-developer part, the part that turns the page brown sucks air a lot. So something is oxidizing in there. Still, mine lasted over a year and still going strong. I keep it in an air tight container un-diluted. How are you keeping yours?

It is my experience that MGIV FB does not tone all that well but the result should be consistent.