I kinda have the same thing with one of my soil plants. I have a pic with a description in my gallery. The only thing I can come up with is I used Mmiracle Grow 3 month fert release soil. The other plant is just in MG Organic soil and loving it.
I flushed the plant once....then have only been giving it ph'd water. Its growing. But all the new leaves eventually curl upwards...not under like in the poster's pics. All the plants I used the MG 3 month fert in have been pulled up except this one. Only because its growing.
All water used has set out at least 2days before being used.