Nothing but PH’d water for the first 10 days. If they look healthy/happy- start them at 0.5-1 ml/litre of the fertilizer of your choice. In 7 days, increase the dosage by half a ml so 1-1.5 mls/litre. In another 7 days increase again by half a ml to 1.5-2 mls/litre and so on/so forth. Keep increasing the dosage until you’ve reached your desired nutrient strength- for autoflowers usually around half strength compared to full strength feeding for photoperiod plants. If you’re finding that they are tolerating the nutes very easily/well or are looking a little hungry, you can step them up every 5th day instead of every week. I’ve always found that increasing every 7 days is safe and predictable and has my plants at full strength nutes by the time I enter flowering. Then you can add all the extras in too if you so desire (big bud, bud candy, whatever, etc). Good luck and super happy/successful growing!