It's never too late, but the earlier the better. Do you know why they died outside so quickly? If they were 4 inches tall, they're still pretty weak and fragile for the great outdoors...

So I'm assuming pre-grown seed is a reference to clones? That's a good idea. I'm figuring you typed inside as a typo, and you meant outside. They should be put outside after they're about 6-8 inches high, depending on if you LST or train. What kind of bulb are you using? I'm interested if the previous dead plants were killed via bleaching.

I'd recommend training at this point, such as LST, it'll allow you to maximize your yield at a late stage. Don't expect much, but at least it's something. Good luck!
-Lay