If the 150 was a halogen then that's why the stretch. halogen bad. I hope the 600 is HPS, high pressure sodium or MH, metal halide.. Going from a 150 to a 600 is alot of stress. Sorry but they kind of look like a lost cause.. If you can take the top of it for a clone cutting and you will be better off than starting from seed again. 2 weeks for clone and you could have a nice little plant ubder the 600.