The browning of the leaf tips is caused by too much fertilizer. One of the problems with powerful ferts is they don't tell you how frequently to use them. The manufacturer expects you to use meters and understand plants well. A soil grow doesn't require alot of fertilizer, just enough to keep them growing and not much more, especially if you're using small pots. Transplanting might be necessary. The short ones look good except for any burning you're seeing. Chances are the only way you're going to stop plants from stretching is to get a powerful light. I'd recommend a sodium type. I know they're expensive, but tying the plants or using a screen of green method to restrict their height might be the only other options. You can also try letting them grow a bit and then cut the top off and maybe this will cause them to grow horizontally the way you need them to.