Simple really.
Just watch your ladies and if they are throwing of little signs of defs then add nutrients. But I wouldn't go adding more, right until you need to. It's very easy to add nutrients and if you do so in a timely manner then you shouldn't have to worry to much but if you add and they don't need it and you burn the shit outta your plants its very hard to take away.
So, watch out for the signs. Brush up on leaf symptoms and so on. And as for soil. You really would be looking a massive flood, down pour for there to be any big difference.
Feed as you need.
Good luck.