Latent heat material model with several compositional fields

Dear all,
I am trying to run models where I simulate the presence of crust, lithosphere, sublithospheric mantle down to a depth of 800 km, and plume (in total, I have 7 compositional fields). I would like to include the possibility for mantle materials to change properties when they cross the 410 and 660 km discontinuities, but I am facing a few issues.
More in detail, I am currently trying to prescribe density changes in the sublithospheric mantle when it crosses the MTZ (and I would like only this material to change density). However, I did not find a way to apply different reference density values for each compositional field. In addition, even though I prescribed variations in the “set Phase transition depths/temperatures/widths” for the mantle only, I realized that other materials (such as the plume field) change density too.
I was trying to use the Latent Heat model for my purpose, but likely I did not fully understand the use of the “Density differential for compositional field 1” and “Corresponding phase for density jump” items, therefore the problem could be there. I have attached one of my files

Rift_Test.prm (13.0 KB)

Maybe someone has any suggestions?
Thanks a lot.
Alessio