Sure ..
People grow apart.
Happens all the time
But, when one party goes from being a "loving" partner on Tuesday, to an "ex" on Thursday, to the prime murder suspect on Sunday ... it is rarely, if ever, about growing apart.
Say "Scott Peterson" softly 8 times.
It is always about a love interest that interrupts the equilibrium.
I can not recall a domestic situation like this that did not involve the 3rd party, in some way.
Once, we locate this person or persons, then the motive and timeline will be one crisper.
It is like gravity ... all these domestics have the 3rd party interest somewhere.