IMHO it will grow better than ever with the 400 watt HPS. I don't see why you should have any problems.Exile06 said:will i have any problem switching my plant that is about 4 weeks into flowering from 2 70watt Hps bulbs and a 100watt Mh to a single 400watt HPS ?? will it just adjust to the light and keep growing or will it shock it.?