setting in p5 can be very strange because one setting for one perameter will require a min-value of something around the order of 1.0+ while other perameter values require a max-value of 1.0- while i agree this is confusing, you cant truely find out the range of a value without test-renders. and in this case, because its a bump map, its onyl stands to reason that you do not need a high value in the bump map. if your issue is that the veins are overpowering the skin texture then post a screenshot and lets see it. otherwise, your values are too high. ( i dont have the bumps your using so unless i see what your seeing, this is the best advice i have)