[LibGDX] Button image strecth issues

hello , i have been using Button with ButtonStyle to draw images on the buttons
the problem is my game screen has a value of (480x800)
so when i play on larger screen resolutions every thing gets stretched/scaled automatically except for the buttons … they remain the same(small).
i think maybe because of the gdx-texturepacker i used to back the ButtonStyle … or maybe it’s some thing else so please can any one help me ?