Well I actually do believe that it would probably effect both, and I recall Ranma coming into contact with the water a few times, though that might just be conjecture. Id imagine there would be more effects on Jusenkyo cursed individuals because of the fact Jusendo is the source of Jusenkyo, and one could assume the magical properties would have some affect on the curses. As for Akane well I can see the argument for her not suffering the same effects, because Jusendo wouldnt have the curse to latch onto but I can see it effecting her as well. '
As I said I can see it strengthening the Jusenkyo curses of those who had been in direct contact with the Jusendo water, with the effect of that being varied. It could change the required temperature, or cause other strange effects regarding the curses. And the thing with Akane is that she only came into contact with one of the taps waters if I recall though as said it's been awhile. Regardless I do agree that it wouldnt make sense for ONLY Ranma to have been effected.
And lol I can elaborate a bit on my original purpose for this, it WAS more a generalized thing but I was specifically wondering what water from Jusendo would do to somebody who had a curse from Jusenkyo, though I am also interested in discussing other possible side effects of Jusendo.