I can't say I have any experience growing this plant but I can tell you that dry leaves on indoor plants are most likely from lack of humidity indoors or foliage that is too close to a heat source such as grow lights. Too much fertilizer can also burn the foliage of plants especially if they are growing in containers. From your description that the plants are getting ready to flower I do not think they are lacking in nutrients. Try increasing the humidity around your plants by misting the leaves or sitting them on saucers of pebbles and water. Keep growing, Marianne Binetti