I would just harvest buds closest to the light,
then you can let the rest catch up.
The problem is you can't flush this way.
since you will be feeding to get the under growth to continue.
You can flush the last of the harvest,
but not the first.
Once you stop nutes,
you cannot start them again
without burning the plant.
So you can't flush for a while
and then start re-growth.
Oh I gues you could,
but it would take patience
and a long long time.
faster to just start over.
Anyway you will be OK.
You can harvest all at once
or let one plant go
for another week or so.
A mature plant will slow down
and eventually stop growing without nutes,
but it will live for months.
.