They usually do NOT need target feeding, you aren't dealing with sun coral!
If they are opening up / polyping out, then your current is fine. A bigger concern is the right lighting. 175 / 250w MH is fine, 400w MH is too much. A bank of VHO's or PC's is also plenty fine.
Most leathers prefer medium, alternating current. A constant direct current will keep them closed, while no current will not make them happy (mucus coat / hard time shedding / accumulation of detritus)..