Yo...I was wandering around in Al B Fuct's thread and came across this quote of his. It just supports what I thought. I think even a little nute burn causes reduction in growth and yield, even if it isn't much. Which wouldn't be something you would necessarily notice if your entire crop is getting it.
"CG, you're right, knowing where to stop can be tricky. There's a bell-curve to this- not enough, just right and dead.
The trick with nutes is to use enough to get plants without deficiencies but not so much as to produce nute burns. Once you pass the peak of your bell curve, more nutrients will cause a reduction in growth.
If you like, you can grow a few plants at the same time that you give nutes of differing strengths to, perhaps 200ppm between each sample, and see for yourself which produces burns or deficiencies, etc. Bear in mind that before doing such testing, all other conds in the op have to be spot on so you are sure that when you see some symptom in the plants, you can be sure it is caused by the difference in nute strength as opposed to something like excessive air temp, for example."
I know it's a fairly obvious thing that burning is bad, but I think people look at it wrong in that slightly burning your plant is giving your plant all it needs and then a little damage to the leaves. It's more than that; It hurts growth and will hurt yield.
I look at it this way. We've all seen how big and compact buds are capable of being, and yeah I know strains matter, etc. But I think 99% of people, including me, don't grow their buds to their max potential for lots of reasons, and this is one of them. I see nice looking buds on plants all the time, but very rarely do you see nice looking, big, and hard buds...because the stuff people mostly mess up on is the stuff that results in achieving the max out of your plant.
These are just my opinions, and I quoted Al B. Fuct because he's someone I think is intelligent and knows what he's doing.
edit: basically, it's all part of dialing in to get the most out of your plant.