Whats the deal with zoey 101?

why is everyone leaving?? first it was dana, then it was nicole, now chase??? Chase is the biggest character besides zoey! do they al hate eachother? Why did dana leave? why did nicole leave? why did chase leave? i want to know the real story, not that chase is in england and nicole is in an all girls school. Do they all hate each other? why do they hate each other? if they do, i cant believe it, because its such a good show ;(