Yes dude that is definateley heat stress, i had the same problem, you need to keep your light at least 24 inches from the plants at all times maybe even more especially when they are this young, you will find that you wanna flower em at about 12-15" though as i flowered my oasis at 18" and they didnt stop until 52" might be different with other strains, but if your in an attic like me you probabley only got 6' of head room, after you take away the 18-24" for the distance from the light and the 18@ or so for the system that only leaves you with around 3 feet for the plants, i found this out the hard way and had to train the little ladies in an s shape as they were to close to the lamp and started to bleach, depends what you climate is like but its summer in the uk now and on hot days with the light on the temp could get to 110 *F so i had to get an extractor works great good for co2 too, a good investment would also be a diffuser then you could maybe get your plants 12" from the light, you would be suprised how fast they grow at the start of flowering, sometimes 2 maybe 3 inches a day, and it doesnt stop till about week 3, any way good luck dude and if you need any help just ask.