You mean feeding nutrients every 3 days, without plain ph'd water in between? How much water did you use when you flushed? When you flush, you should be using at least as much water as the size of the pot (i.e. 3 gallon pot, flush with 3 gallons water).
Are the plants dry in 3 days? It is tempting to think that if you don't even use a gallon every 3 days they should not be overwatered, but that could still be too little water too often if they never dry out. Also, when you water, you need to soak the pot, not just water it, otherwise the roots don't all get water.
The amount of water a plant uses all depends on size and age of the plants, genetics, ventilation, temperature, humidity and method of watering. On top of that, it is extremely important. The worst thing you can do is water too little, too often. That is why I use a scale. I have a friend who waters a quart every 2 days, and his results are less than desirable, to say the least. Terrible, actually. But he won't listen, and keeps right on doing it.
Your plants could actually be suffering from nutrient toxicity, without more information it is hard to say. At the very least, you should be watering until you get 20% runoff water, every time you water, to prevent salt buildup in the roots. Yes, it is a pain in the ass, but otherwise invites problems.