distance from light source looks fine.. the leaves are curling possibly because of over watering and/or nute burn.. I do see a few yellow specks on the leaves so it points to over feeding... I would flush them with distilled ph nuetral water before night fall then just water them every third day or so.. never let the soil completely dry out BUT if the soil is moist to the touch (at all!) then do not water.. remember.. even only an inch or two below the surface is much more wet than the top... good luck!