tinytoon,
That's what I do and my plants are turning out pretty darn dank and thick.
During Veg I add part A only ph'd even when I don't add parts B and C.
So far my experience has shown me that it's not an exacting science to the point where harm is done unless there is a gross mistake. I actally only have changed the rez once so far, when I flipped them to 12/12 and switched over to the flowering ratio. No saying that this is how you should proceed, but rather that DWC is that forgivable in respect to rez changes.

I'll swap again about 2 weeks before harvest to flush the nutes and make them more smokable, just ph's water...

my :twocents:

M.P.