Starter rising but then falling

Hi yall I’m at about day 31 and my starter has just recently began doubling in size within about 4 to 6 hrs of feeding a 1:2:2 ratio with all purpose flour with one feeding a day . so I was prepping to make my first attempt at making some dough but I noticed today that it is falling back down pretty soon after it’s is rising to 2x its original size. Does anyone know if this is normal and if not what can I do to fix it?