I would check it before re-using it. Just to make sure its OK. If the Ph is not OK, coming from RO water doesn't make it any better than out of range fresh water.
has worked fine for me at 6.8 for over a year now... 6.8 and 7.0 are very close, i know that pH is a log scale, but still, it is very close and has not made a difference in my grow room...
your r.o. water should be fine. but if you add any nutes check the ph. my r.o. water is 0-3 ppm 7.1 ph. when i add nutes it goes to 1100-1300 ppm and the ph drops to 3.6!! so i have to use Ph UP. i ph my r.o. water when i'm just feeding water and no nutes down to 6.5.