If you did not presoak the rock wool the lime content it comes with could be infecting your soil and skyrocketing the ph.

ms stands for microseimen. I think you may be talking E.C.

1 EC = 700 ppm
700 ppm = 1400 microseimens

What are you feeding?
Sparrow Reviewed by Sparrow on . brown tips, light burn? Ok, new grow, browning leaf tips, is the light too close? Just the clones are doing this, they do have roots already. mS is under .90 (my water has a base mS of about .25). It is the old growth that is yellowing, and for the time being the new leaves seem to be coming in fine, but time will tell. Rating: 5