Grower at 6-10 weeks. I'd buy a bag of grower next, and mix some together to help them make the switch. You can get fussy and give them 25% grower and 75% starter first, then 50/50, and so forth. Or just dump some grower in the starter, then give the grower.
Depends on the brand you use. I use Kent which covers birth to lay- about 20 weeks. Purina has a starter and then a layer also. I think the bag will give you guidance or see what the feed store carries for you.