Hi there all undercover PhD Agronomists,
I'll rephrase what I meant by "nutrients going out of whack if you don't change your res" to be more technical for all that want to get more in-depth info and didn't like my PG-13 version.
Plants indeed do not eat what they want to eat, the plasmodesmata works a little more complicated than that. Nutrient absorption in plants works via osmosis, polarity, and ion exchanges. And they do, mostly eat, what we give them. BUT NOT NECESSARILY in the ratio that we give it to them. For example, if somehow you had a nutrient solution that had 10-10-20 NPK, plus 5 Ca, 5 Mg, and 5 S, and 1% Fe (JUST AN EXAMPLE MIX). It doesn't necessarily mean that your plant will be absorbing everything exactly how you are giving it to them and in that ratio, Why? because ions do not freely exist in the world, elements exist only as molecules to find equilibrium. Some molecules are easier broken by plants than others are. For example, the plant will more easily consume Nitrogen if the raw ingredient was Calcium Nitrate than if the raw ingredient was Urea. It takes longer for the plant to turn urea into absorbable nitrogen than it does when it is already in a nitrate form.
Also, every strand has a slightly different metabolism and nutrient companies make GENERALIZED formulas with different chelator molecules like EDTA and DTPA, fulvics and a variety of plant extracts such as
yucca that further aide in faster absorption of SOME elements like iron, magnesium, calcium, and phosphorous; but not others like nitrogen and potassium.
So, when I gave you all the PG version I was wrong to do that and I should have written this long ass essay about it. But when you say that ALL PLANTS eat/consume equal amounts of the ingredients found inside of the bottles just because you are feeding it to them - you are even wronger. They indeed don't chose, WE DO IT for them by feeding them the nutrients; and in turn, the nutrients themselves send the entire solution out of whack after about two weeks. The plants by far will also consume way more water than they do the nutrients dissolved in it, this means that the concentration of solute to the solvent will increase (the TDS will increase), making the solute go further off track; Calcium will bind to sulfur making Calcium Sulfate, Iron will attract to Sulfur making Iron (III) Sulfate, and the Carbon from most of the plant extracts that are sure to be found in all of these nutrients will make Calcium Carbonate and Magnesium Carbonate - all of which are either insoluble or very difficult for plants to breakdown and consume.
SOLUTION: Change the res every 2 weeks for optimal nutrient delivery and add pH'ed water frequently to your res to avoid these molecules from binding; unless you are an undercover PhD Agronomist like heisenbubble.