I also started to treat with fluorish, fluorish excel, and Seachem root tabs and again saw no change in growth.
I have brought this issue up on a different forum in the past year.
Who in all creation decided that Flourish Comprehensive would save the day?
Macro's are in much greater demand for plants than micro's.
I have no issues with the quality of Seachem's products.
They also profess a very lean dosing schedule to CTA.
Is it the people in the LFS that sell this to everyone?
I am unsure, LFS near me tries to sell everything to anyone. Salesman Technology I guess.
Sorry for my rant.
Back to original issue.
No two tanks are alike even with the same source water.
I have a 55G that will kill any java fern I put in it, go figure.
It grows crypts better than any of my tanks even with an inert quartz substrate.
Macros as in NPK, Nitrogen, Phosphate, and Potassium are the largest consumed elements by aquatic plants.
A loss of one of these elements is most likely causing a stall in plant growth.
To explain recent growth in the other tank, these elements are not yet depleted from tap water introduction.
I would recommend a more complete fert regime.
PPS Pro or an EI solution.