Reviewing the discussion to date on this thread, and based on gamut testing I've done in the context of my various printer and paper reviews for this website, I am landing on a high probability that Tim Lookingbill nailed it correctly in his post #37. I do know that between an Epson 4900 (very wide gamut capability) and an Epson P800 or Canon iPF Pro-1000 (narrower range of gamut capabilities compared with the 4900), there is a reduction of gamut potential and the colours that most bore the brunt of that were in a narrow band of bright green to yellow-ish. This seems pretty close to some variants of jade, and therefore support's Tim's observation.
So, the path to a solution that occurs to me is to try to eek-out the widest possible gamut rendition you can from that iPF8400, which of course raises questions about the capability of the iPF8400, the gamut rendering potential of the paper and the "reach" of the profile. So I had a look at all this for you. Because Canon's website is a train-wreck for finding such things, I went to Ilford's instead, where I easily downloaded their profiles for Gold Fibre Gloss (a very wide gamut paper) for both the Epson 4900 and Canon iPF 8400. Then I compared these profiles in ColorThink Pro, and here is what I found: for the 4900, gamut volume is very close to 978K. For the iPF8400, gamut volume is a tad over 880K - hence considerably less gamut on the IPF8400 for the same paper. Then the question is, where does the gamut take a hit on the iPF8400. For that, a three dimensional diagram generated in ColorThink Pro helps a lot. Please see the illustration, where the multi-colour is the Epson 4900 and the solid red is the Canon iPF8400. You will see that in the full range where that jade hue could fall, it may just be out of gamut for that printer/paper combination.
I have also determined from my prior research that making custom profiles - with high quality profiling equipment - can often expand gamut relative to OEM profiles. So perhaps your next step would be to either make or order a high quality profile for the widest gamut paper you can use and see whether it eeks out enough to reproduce the jade more correctly. Wide gamut papers would include such as Ilford Gold Fibre Silk, Ilford Gold Fibre Gloss, Hahn FA Baryta Satin, Canon Pro Luster, Epson Legacy Baryta, Canson or Epson Legacy Platine, Canson Baryta Photographique, and there are others. The custom profiling should be done with better than a Colormunki. If you don't have an i1Pro and i1Profiler, I would recommend using a good custom service that does. If you do not have ColorThink Pro for analyzing the profiles you are now using or the one you eventually order, you can send them to me and I shall read them for you. I do suspect we are closing-in on a gamut/profiling issue that just happens to hit that part of the spectrum a bit hard. The only other thing I can think of is that the spectral properties of the paint are such that conventional ICC profiling targets are not well-adapted to the subject matter at hand. I have also seen this issue some years ago. But I suggest first seeing what is the best that can be produced from that printer and a really good profile on paper that has very wide gamut rendering potential.