No big deal bro! I've seen the same thing happen before. Just wait and watch the fun. All the other leaves should be fine. I would triple check for pests though. If you have something eating one side of a baby leaf the other side keeps growing and creates the spiral you are seeing. Yours is probably a birth defect though...
Also, as the plants use water, your res level will drop. As the water is used up the ratio of nutes to water changes so you PPM always goes up until you add the same amount of water the plants used. Draw a line on your res and fill it to the same spot every time. Then check your PPM after the res is full. If everything is correct then you should see the PPM drop a little. When that happens just add more nutes and you're good to go.
I run my PPM level based on what I see happening with the plants. Every strain is different. Some strains like a ton of nutes and some freak out with just a normal amount. On my current grow I have some plants that are light green and want more nutes than I'm giving them. In the exact same mix I have other plants that are showing signs of over-fertilization. And just like that bitch Goldilocks, some of the plants are just right
!