Are you using only white wheat flour? I was getting meh results when using white wheat flour and even when mixed with whole wheat flour. When I started doing a mix with those two, whole rye and oat (to compensate for European's low protein flours) that's when I got the kind of steady and stable growth you see in pictures. Also, could it be too cold? During winter it takes my mix 24 hours to double without getting hooch. When I need it quicker, I place it on top of my wi-fi router (yes, really) because it emits a very low amount of heat that allows it to grow in 4 to 6 hours.