Thank you, fellas! After taking some sleep I found a small issue in the marmoset viewer file. Due to the given extension time, I updated the lighting a bit. Nothing major, but it troubled me.
like I said amazing work mate ... can I just ask you how did you approach the texturing process ? Did you do materials ID before jumping in Substance Painter ?
Thanks! Yes, exactly. I baked material IDs from my base mesh and added some missing detail colors missing from the sculpt. Then did the rest in Painter using smart materials and masking. I just baked my own (cleaner) normal maps and AO, not the Painter generated ones.