Get the fox farms hydro nute chart and follow it... since autoflower plants vary adjust accordingly. If you aren't using ff nutes you can still get an idea of what fertilizer and when

I started with a 1/4 dosage of flowering fert while my plants were seedlings and they are doing pretty well. I didn't have the budget to buy fert to use for just a few days of veg. I am currently using tigerbloom at 1/4 dosage and big bloom at 1/2 dosage. The big bloom is just batshit and worm casing so you won't get burned from it. Watch your oh though