Most all "weeds" are broad leaf and the poisons in the "fertilizers" are formuated for broad leaf "weeds", or any plant not grass. Crab grass is different and those controls are fairly specific for crab grass, but most all the broad leaf "weed" killers will kill any broad leafed plant, including milkweed. Seldom are these things really needed since good lawn care will keep most all "weeds" from growing in healthy turf stands. Mow high, which helps shade the soil so "weed" seeds do not get the sun most need for germination, and exposes more grass leaf to the sun so they manufacture more nutrients to feed the grass corwn which will in turn send out more grass blades to pick up more sun to manufacture more nutrients, so the turf grows thicker and crowds out the "weeds" that might try to grow there.