Weird shadows on sim's arms with cc top i created

Heya guys, this is my first time creating an actual mesh for the sims instead of just poses, so i've gotta say i am surprised at how smoothly things have been going. I've had very few issues in the creation process, save for this one... thing i'm encountering with this cropped top i've created. It's just a simple mesh edit of one of the base game short sleeve t-shirts welded together with a nude top so she didn't have any gaps, and then i went in and painted my own texture over it. However, on the arms where the sleeves end, i'm noticing these weird shadows. Now, if the sleeves weren't so tight to the body, it wouldn't be an issue, but they aren't actually as flowy or long as the shadow suggests, and i'm wanting to create my OWN shadows, so it's interfering with that. Here's a pic of my mesh in CAS:
https://gyazo.com/faff5164c5d36963683fc5b1f8889239

and here's a pic of my shadow maps (which are literally empty) in sims 4 studio:
https://gyazo.com/026155f82d0ba5d1f7623e31bf0d10aa

as you can see, the weird shadows are even visible in the catalog thumbnail, so i'm really just not sure how to get rid of them. any help would be greatly appreciated. thanks a million guys ♥