Even a 5 mph wind can move a pellet at 30 yards a surprising amount. I did not appreciate it until I was trying the 30 yard challenge. I wasn't happy with my results and ran chairgun to see how much wind could be moving my pellets. Especially for a day to day movement, wind is a possibility. It doesn't take much with a pellet. Wind can cause elevation shift but I still think of it mainly as a horizontal issue. If your groups shift in the direction of the wind, even light wind, then you may have found your culprit.
Hawke Vantage scopes can have parallax adjustment, my 2-7 on my Prod does. They are my pick for an inexpensive airgun scope. None of my scopes are expensive, however. I have a West Hunter 4-16 on my Avenger, an Athlon Talos 6-24 on my P35-22, a Primary Arms 4-14 on my P35-25 and a Primary Arms 4-16 on my P35-177. All except the Hawke are side adjust parallax which is handier. All go down to no more than 10 yards. I hunt at 6X but more magnification is handy for target shooting.