How to decide when to give water only till harvest with liquid organic nutrients

Depends on how much time is left (a guess) and how healthy your canopy is... the weaker it is and the more damage in it just means it can't mitigate the loss of nutrients provided. Do they bother flushing the earth outside? This isn't 'evidence' but it is common sense. IF flushing was so important, then why isn't all outdoor weed ruined because it is not flushed? Do it to be lazy, but don't do it because you think it has some profound effect on the outcome. It doesn't change mineral content of the flower material. Same levels of building blocks because the instructions to build flower are dictated by DNA sequences and not what happens to be available. Also, there is no excretion system, so that stuff that was used in the construction of flower isn't going anywhere. i wouldn't overthink it. If you want to give water only, just make sure the canopy doesn't deteriorate too fast.