Hi, purchased new Schwalbe ultremo zx just after Christmas, and only riden on them twice. I have noticed fine cracking on top side of sidewall most of the way round. You have to get close in to see it, but noticed it mainly running through the white graghics on the tyre wall. They have been inflated properly. Is it something to do with how the different compounds meet, or is it a trip back to the shop?