Too much of a nutrient, like nitrogen, will burn a plant. Too much nitrogen in water leads to an explosion in algae blooms, which suck all of the oxygen out of the water, killing everything around them. The nutrient is to benefit whom? Too much of a limited thing makes a limited thing grow, which antagonizes everything around it.
Similarly, too much love and affection on a single person in a group will turn the others towards resent, or at least cause them to angle towards that love in antagonism with each other. Needless to say, too little of a given nutrient is detrimental in the opposite direction; nothing should starve either.
And nutrients do indeed move unevenly, at different times and through different regions of space.
