Well Gardenking, fertilizing every watering is the exact nature of hydroponic growing.

I grow in soil though and DO use fert every time with the exception of leaching. You can't get nutrient lock through salt build ups if you over fertilize. I have not had this problem though since I flush with lots of plain water every 3-4 weeks (2-3 times during flowering). If you have good drainage this will work wonders for stability. Overwatering is a matter of how often (not giving plants time to use the water in soil and keeping it too damp too much of the time) not a matter of how much at once. Soil can only hold so much and the rest drains away. A good flush will keep your plants healthy.