It could be carbides that don't go all the way into solution. 1084 is a euctid(sp?) steel, meaning the amount of carbon in it is perfectly balanced and will all go into solution as soon as it hits critical. Since 1095 has extra carbon, it needs a slightly higher temp and a short amount of soak time to fully disolve the extra carbon. If you're not disolving it all then you have extra carbides floating around in there, which with light sanding and etching can become visible.