Light cooked plants??

I added a 300 watt standard light bulb (outputting 6120 lumens) to my plants. Within 3 hours, the plants were completely fried. The light was about a foot away from the plants and had fans blowing on everything.

What caused this and what should I do differently next time?

Never use a standard light bulb for growing plants. That's a mere 20 lumens per watt... the rest is fucking heat. 120 watts of CFL would dominate that shit easy, and cost less, and your plants would still be alive.

Fluoros or HID are your main indoor choices. Both are pretty effortless to grow with.