If your numbers are rising like that (starting at 1000 and ending up at 1400) then your plants are drinking a LOT more water than nutes. I would drop your number back further then......perhaps down to 800 if they are using up that much water and leaving behind that much nute in your solution.

Quite honestly I haven't really had that problem to a large degree.....I tend to keep my numbers fairly low all in all and generally while the rez amount will drop the numbers tend to go DOWN so I have no trouble adding fresh full strength solution. One of my plants is in week 6 and is drinking over a gallon a day so it's easy to keep up with that one by just adding a fresh gallon a day.