I'm thinking the blue silkie is a girl and so is the black maran, your first chick that I think you have already sussed is a boy as is the white silkie so it does look like 2 and 2!
pheeeew i was getting bit worried there for a min ,so is the black one a maran then ? i was told it was an orpington when i got it at a day old grrrrrrrrrrr she is realy sweet though