Well this is what I did. Take it with a grain of salt but it has worked out well.
My first week or so of Flowering I use Veg nutes going from full strength down to 1/4 strength. I then go to flowering nutes starting at 1/4 strength and increasing to full strength over the next two weeks.
I try to do things gentle with my girls. Nothing too sudden and no surprises.
Like I said this is just what has worked for me. I have had no issues with nute burn or lock out.
Happy growing