Picture suddenly gets Paler

Hey,

My problem is as follows. Sometimes when I paint and then blur colors, somehow the rest of the image becomes paler. I've already looked for solutions in the app and haven't found anything. The only solution is to go back until the whole picture is normal again. Strangely enough, it's not the whole picture that turns pale, but only a certain area. Im on an Ipad btw.  I also have a picture of the Old Black that Suddenly gets paler and a new Black.

Thanks,