If you do EI for a week or two, that will rule out the nutrients, then you just have CO2 to contend with.

If new growth is small, shortened etc, melting , it's very likely CO2.
If you use EI, always look there first if there's algae or other issues, you can always do a mid week water change and more than 50% if you suspect anything and reset the tank.

Then check the CO2 carefully.
Excess CO2 will never hurt the plants, it'll just gas the fish.
So if the plants are hurting, most often it's due to the CO2.


Regards,
Tom Barr