should i be concerned

Got a second hand bike and noticed a crack running down the seat tube after I took off the reflectors .-. Should I be concerned? This is an aluminium frame bike and I know that the inflite was designed to flex but I wasn’t expecting it to crack. I’m really hoping it’s just a paint crack since I can’t see any distinctive stress marks in the down tube. I’ve been advised to purchase a new frame and transfer the parts over but I’d like to hear other opinions before I do it! Thank you