Kinda looks more like an overwatering problem or disease.
Over ferts usually gets you massive leaf drop and yellow leaves.
Edema or whatever it's called.
Fert burn kills roots fast but you get instant yellow leaves that drop as you water.
As stated above what are you using for ferts.
The white veins look like edema or fungal stuff to me from over watering.
Maybe too much ferts are part of the problem but I think water is also a problem.
Maybe drainage?
Soil doesn't look very porous.
I use 1/4 ferts everytime I water,BUT I water until the water runs out of my cells,pots etc.
Fert burn usually leaves you with leafless stalks.
The white blisters looks like water problems to me or a soil issue-fungus or whatever.
Maybe dig out the start and see the roots.
IF they are white then just put in new soil.
Go from there.
If it is ferts bare rooting could save it.
IF it is overwatering you can save it too.
I'd bare root it and check it out in new soil.