Hey Reef,
Sorry to hear about your plant(s), I think a little more info on your set-up will help some of the experienced famers here to better diagnose and potentially fix your problem (i.e., light distances from canopy, room/tent temps/humidity, ventilation, fans, etc..). In my experience when the damage is only towards the top of your plant, its probably heat stress (especially considering the fact that you just introduced a 1000watt heater to your grow area). Plants that have water/moisture readily available can sometimes counter the effects of the added heat by simply expelling more moisture onto their leaves which assists in cooling of the plant. It would be my guess that your issue is a combination of light too close(heat) and not enough moisture(cool) to help the plant deal with the changes you made as well as some ventilation/fan issues.
Things to try: -Put a little more distance between your light and canopy
-Water a little more to counter the new heat you've added to your grow..Also, "completely" drying out your soil
IMO is not good to do, soil should have some kind of moisture to it at all times...
- Good ventilation, especially fans blowing in-between your canopy and light source(s).
Hope this helps a little..DB