There are a lot of folks on this site that have a good handle on this hydro thing.
What Mimbres valley is saying about rapid Ph change is correct, far less harm is done by a Ph out of range than a rapid correction of Ph. He is spot on about the EC staying relative to water use being the sweet spot. unfortunatly its not the same for all strains.
A Ph of 6.25 is not that far out of range though and changing out solutions every 10 days, only benifits the hydro chem sales people.

I would still run them on Phd 1/4 strength nuits for a while

The clawed leaves is indicating TOO MUCH nuits.

again I find that an EC of 0.5-0.7 is the best range or 450-650PPM

Daddy