... they seem to lie under the surface and on occasion appear as if by magic. i dont think you have anything to worry about terra, youve been peing for a while now. your vein structure may have only just decided to show itself.
I have noticed some new veins as well during PE. My penis was not very veiny... but now the veins are more noticeable. Suppose the increased blood flow and engorgement during jelquing makes them stand out more.