Are you adding calcium and magnesium to your nutes? Most bottled nutes don't have enough cal/mag for ro water and if that's the only thing you changed this grow (ro water) I'd bet that's the issue. I'm no expert and just trying to figure this growing thing out myself but it will be easer for people to give you advise if you tell them a bit more about your grow. Strain, grow medium, nutes, ect. Take a look at some pics of calcium and magnesium deficient plants and see if you think yours look like that. Some people like cal/mag combined supplements and others like seperate calcium and mag supplements. I hope this helps and I hope your grow goes well...Fiddy.
A little more information would help. What medium are you growing your plant(s) in? Do you know what your PH is that you've been feeding at? Did you let your RO unit run for so many gallons like most RO units recommend before using the RO water? The lower ppm your RO water the more the PH can swing due to it not having anything to buffer the PH. I have found adding an amount of tap water into the RO water of the mixed up solution can help even out the PH.
My first thought from looking at that picture would to be to look for bugs as my first step and then expand to other possible issues like resent changes in water/food/environmental changes, ect.