Welcome to BYC. You can start mixing a laying ration with whatever you are now feeding gradually increasing the proportion of the laying feed - or can you can follow Kelsie's suggestion of feeding a 'flock' type feed with oyster shell on the side. 3 rooster is more than you need, 1 is probably enough, but with 2 there is a back up if something happens to one of them.
First
X2 on sourland
I usually wait till one of them produces an egg I know waiting is hard but mixing it in slowly works as well
And having a back up rooster is always a good idea as predators are always lurking and are just waiting for the right moment like a single rooster and you are expecting fertile egg's when it happens roosters will protect their hens and this is how they go
Just a suggestion no one is telling you what to do
gander007