The Buff Orp should be laying at around 6 months old, the Silkie EE mix might take longer because silkies take awhile to lay eggs but EEs do start around 5 months old so she could lay earlier. The Welsummer will lay at 5-6 months old, mine started at 24 weeks old.
Hello and welcome to BYC! :welcome
A signs when your girls will be close to laying are bright red combs and wattles, also you could feel their pelvis bones, here's an article on that.->
https://www.backyardchickens.com/articles/who-is-laying-and-who-is-not-butt-check.73309/