Yeah I wouldn't worry about it. Every baby is different and hits milestones at their own rate.
Ariel isn't trying to stand yet. She loves to stand when you hold her though. And as far as crawling goes, she's not super interested yet. I put her on tummy time and she doesn't mind too much and can push up on her arms but hasn't quite figured out she needs to pick up her legs too! Oh well. She sits up really well though. She can sit up for like, 30 minutes and not fall over. I'm proud of her, heh.