Phloem
The living vascular tissue a plant moves sugars and dissolved nutrients through. It runs in whichever direction demand pulls, unlike xylem, which only carries water upward.
A plant runs two transport systems. Xylem Xylem The vascular tissue that carries water and dissolved minerals from root to leaf. Flow is one way and pulled by transpiration, so anything that slows transpiration slows delivery. is dead tissue at maturity and carries water and dissolved minerals one direction, root to leaf, pulled along by transpiration. Phloem is alive, and it moves the sugars made in the leaves out to roots, stems and flower, along with whatever nutrients dissolve into that stream. Its direction is set by wherever the demand is rather than by a pressure gradient from below.
Not every nutrient can ride it. Nitrogen, phosphorus, potassium and magnesium move freely in phloem, so a plant running short will strip them out of old fan leaves and send them to new growth. Calcium, boron and iron essentially cannot, so a shortage in those shows up in the newest tissue while the old leaves stay clean. That is why tipburn on fresh growth points at calcium and yellowing from the bottom up points at nitrogen.
Calcium is the one that matters in an enriched room. Because it barely moves in phloem, it only arrives where transpiration carries it, and elevated CO2 closes stomata and cuts transpiration. Same tank, same feed EC, less calcium landing in the tissue that needs it.