it's difficult to say for sure without knowing what has been fed in a higher resolution t han the info growdiaries gives. dose and initial concentration varies, so 2ml per volume doesn't paint full picture. depends on what was in the soil to start too. hopefully, their soil mix is consistent from purchase to purchase so you can gain familiarity - preempt any issue in future with decent predictability.
i see potential Mg deficiency. i see what could be a blue tint to leaves which hints at a P deficiency. A toxicity of some sort could cause both.
I don't see any spots to indicated a Ca deficiency, but those symptoms show up many weeks after the deficiency is occuring.
Some heavy clawing which could be a sign of too much nutes in substrate, unless it was just given tons of water or limited drainage in soil causing droopiness. less than 1/3rd perlite or similar and better to be closer to 50%. almost impossible to cause overwatering droopage with good drainage.
do you let it sit in waste water, if so, stop. put it down drain or toss it outside.
So any variables.. any specific answer given with oveconfidence is suspect.
as far as recovery -- some things heal, some do not. necrotic, rust, and other severe damage will not heal. interveinal chlorosis or paling should reverse. basically, if the plant material in question is dried up or brittle, it ain't healing. It will be healthy before these things are fixed... trending in right way means you got the equilibrium back into a safe zone. healing damage will be a longer term project for the plant, but the tox/def is gone/mitigated for that to start.