I experienced the same problem 8 or 10 months ago, when I bought a new pot. I was able to salvage some value from the new under-pigmented pot by transferring some of it into the old one (which wasn’t empty but had lost enough medium that it was acting more like paint than a wash). The mix was more like what I was after, but I won’t be buying GW’s washes again. It’s a shame because their previous version performed quite well.