I just bought a female budgie and her cere is brown and a bit crusty does this mean shes in breeding condition?

im wondering if this feamle budgie i bought yesterday is in breeding condition because her cere is brown and crusty..i have her with 2 other birds one is also a feamale and the other is a male..they seem to be showing alot of interest and making alot of noise like flapping wings ive never heard this kind of behaviour before..im wondering if they are mating or what...should i get another large cage for them and put them together to breed...she is on a good diet but i just started her on it like oyster shell and also im going tobe puttin a uv light where the birds are.....should i wait to make sure she has enough calcium and proper diet b4 breeding her and how do i know when shes got the proper diet and is ready...could it be to late maybe they mated already.....what else can i do to get my budgies in breeding condition and how will i know...i want babies but i dont want egg binding happening...plz help...i know that when a female budgies cere is brown shes in breeding condition.. how long does it take to get enough vitamins in her to breed and as well as my other female budgie