Thanks for the heads up, LOC, I have heard about the topping off. I change my reservoir every saturday regardless. I refill with half strength nutrients. That puts me at about 1500 ppm already! So Sunday Monday Tuesday I top off with pH'd water and continue to hold reservoir pH at 5.8. Then wednesday I make another batch of nutrients and top off with 1 gallon of the mix per reservoir. Then top off with water until Saturday.
I figure this way, the plant gets an opportunity at full strength nutrients over the course of the week rather than getting shocked with nutrients on saturday and slowly processing all week. It keeps the ppm low, and that's why I think I may be able to add a little more of something.
I know this method may be somewhat wasteful or something but I haven't had any nutrient stress this way - not even tip burn.
I also added Bud Candy (magnesium), tho so that helps with the nutrient burn...