Looks to me it is definately heat stress and / or humidity issues. If your humidity is between 40-60% then it is a heat issues. Leaves curlin on the edges to reduce surface area for light exposure to try and compensate. I would definately pull your light back. I also noticed you said you flushed them. The symptom can also be a sign of over watering. The biggest mistake on growing is to over water. My rule of thumb is (along with many others here) let the top lay of the soil crust over and look dry before watering, and when you do water....the run off should be about 10% to reduce the build up of salts in the soil.

GTD