How often should I fed them?

I would suggest water, water, feed, water, water, feed as the best routine in soil, so they are being fed every 10-14 days. Watering every 2-3 days out of habit may not be best, watering only once the top 1-2 inches are dry, is much better. Boosting growth by extra feeding will not work with autos growing outdoors. Autos need bulk light - 18 hours all throughout their entire life cycle to perform reasonably. Sadly, growing autos outdoors with only 9 hours of light will only result in dwarf plants flowering at around 4 weeks and producing minimal yields. Autos in my experience, are really best left for indoor cultivation. Starting your outdoor autos around mid May, has in my experience, led to the most productive plants, albeit, still small and not a patch on any photoperiod plant. It is due to poor yields that I gave growing autos away, a long time ago, and I still think they are "joke" plants that any real grower wouldn't waste their time on growing them, ever! Hope this helps,........ Organoman. (and sworn enemy of autoflowers!)