Fertilizing my autos did much more damage than helping, and I had them in organic soil. Next run will just be in organic soil and watering only. I'll let the nutrients in the soil feed the autos, no need to add more for autos. Picked up some Mephisto autos for my next go around. There is a real learning curve when you try autos for the first time. Good luck with yours.
I think the no fert thing holds true for all plants that are done in under 12 weeks! Modern potting soil is already pre-fertilized. If you're making your own mix, it's probably nice and hot as is and doesn't need anything else!
Mandala Mike suggests only feeding when you see a need for it, and potting up is usually a better measure than feeding. That's the tactic I'll take on my next run; three girls in seven gallon pots and I'll only water in with pH adjusted water!
I'd like to try the Mephisto stuff some time. What did you get?