Pit bull

Any other pitty mom's out there? We've got our 6 month old Rebel(red nose) who I call a horse lol and my Ninja(black and white) who is only 12 weeks old now. I'm so worried that she's too small! She's a razor edge pit so my boyfriend says she's supposed to be small I'm just worried. She's smaller than all our cats even my 8 month old kitty! Any other pit enthusiasts with advice/ input? Thank you!