Switching formula

So recently I posted about us giving my daughter Miralax per doctor request. Well we decided we wanted to stop doing that so we got a different formula tonight. Yesterday I gave her Miralax and it made her go a couple of times and of course it just kept coming like usual. When that stuff kicks in its like we go thru 3 or 4 diapers before she stops. So we got another formula and gave it to her starting last night and she has pooped after both bottles so far. So now I'm not sure if it's the Miralax and new formula kicking in or what and if this is gunna make her go after every feeding. That's not exactly what we wanted but we didn't want her relying on a stool softener either or anything else for that matter. Idk if I just need to.wait it out and see if it's just because it's new or if I should mix this new with the old. Both at Similac brands.