Friend Advice

I used to be friends with this group of girls and we hung out all the time ( we do the same sport) , I got them friends with all the boys in the sport too. Then I decided I didn't want to be in the group anymore since I was the youngest and decided to be friends with people my own age. Now the group has gotten bigger and closer and I regret leaving it. They all are nice girls but they don't really try include me in the group anymore, they aren't very welcoming. Anyways, can someone give me tips on how I can get back talking to them ? I was just in a bad mood one week (period) and I made a pretty shit decision and I dunno what to do