Hence the "I give up"
OK Stickers do not breath,You get a build up of various chemical gases in minute quantities between tank and sticker. This leads to pressure or chemical reactions lifting the sticker, precursing the intake of atmosphere leading to more hygroscopic absorption of airborne chemicals. That is on a stationary tank ,yours at times is rough motion and being subjected to stretching rubbing and many other violent forces, compounding the loss of adhesion. If it is a metal tank or fiberglass (unlikely )get a competent airbrush job painted on it ,if it is plastic your stuffed as ALL plastic tanks actually breathe via osmosis through their shells.