I do have to poop when my addy kicks in but I don’t have diarrhea because of it. I had that with concerta (I switched years ago because it just wasn’t effective enough for me).

It's absolutely the meds. I took Adderall for many years and it always did this. I now take Vyvanse but it's about the same with that one. Amphetamines in general will make you have to poop

Stimulants are well-known for making you have to go to the restroom more. I've heard people talk about needing to go take a shit right away being a sign their cocaine is pure. Basically anything which speeds you up is gonna speed up your metabolism, too, meaning your body forces out more waste. Personally, neither my Vyvanse nor my Adderall seem to mess up my gut anymore than it's already wonky with my IBS, but I definitely notice I pee a whole lot more when my meds are in effect. I'll also notice my meds kick in sometimes by getting a sudden pang of hunger.