Thats much better as an option.
Awesome because even de-clorinated tap water turns bad quicker than nice filtered cold RO
A little high depending on what its consisting of . but that could be ok to top off on if it wasn't for my next statement.
The res /res's need emptying cleaning a disinfecting also the rockwool cube needs the algae killed off as its suffocating the root zone. and infecting the res's
Getting close to your limit as long as it doesn't exceed 69.8 by lights out , or at anytime.
You'll be fine running higher to a degree but it will start to cause damage to the root zone weakening it ,also decreasing the dissolved oxygen in the solution allowing algae and then the pathogen Pythium to grab hold. 69.8 is your limit.
Overall my suggestion is to flush the Rockwool cubes with a h2o2 solution following the directions on the label ,don't pour directly onto the cubes. I researched this briefly and for this to be fine to do as i ,again ,have little to no experience with Rockwool because it was one grow over ten years ago. Research this thoroughly before continuing.
Another thing id like to mention is why i choose not to use Rockwool. And that's because dangerous to your health if inhaled and causes scaring of the lung tissues. therefore i personally see no use for it myself but that's my own opinion.many still do with great results.
i hope this info helps bro