We live in a semi-detached house with bay fronted windows upstairs & down (5 window bays). We recently had the old wooden windows replaced with new UPVC ones. The work was done by a reputable company and the bays were fully supported with steel rods during the work. However, I now notice a small hairline crack on either side of the upstairs bay window. running from below the window sill on either first window bay, to the skirting board below. There are no cracks on the downstairs bay, nor anywhere else in the house. Is this normal after replacement windows? The cracks look quite small and I can't see any cracks on the outside wall. Any advice would be welcome. Many thanks.