Tank is thriving, except for one plant. (Echinodorus horemanii red)

[sleepycloud122]

Hello everyone, I would like to ask your opinion about something that I can't find any information since this plant is rather rare.
My tank has: Helanthium tenellum red, Eleocharis montevidensis, Echinodorus grisebachii Tropica, Echinodorus Red Diamond, Echinodorus aquartica, Najas Guadalupensis, Egeria najas and Lemna sp.
When I originally set up this tank I also put a beatiful little Echinodorus horemanii red. This plant however never took off. Its leaves are becoming transparent and melting.
Tank specs: Twinstar C III (40cm) 60-65% volume, WIO Eonian substrate with Growcap root capsules topped with sand, NO additional fertilization because the botanicals and fish waste make up for it.
What am I missing for the little Echinodorus to thrive as well?

 

[Wuestenrose]

Hi Vagg,

do you have pictures of your little suffering beauty?

Greets
Robert

 

[sleepycloud122]

Hi Vagg,

do you have pictures of your little suffering beauty?

Greets
Robert

You can see it on the left of the grisebachii tropica, on the center of the tank

 

[Wuestenrose]

Looks a little bit dark, the tank... Red plants usually need more light than their green counterparts


Br
Robert

 

[sleepycloud122]

The red diamond is growing nicely, the Helanthium has produced lots of red stems too...

 

[Zer0Fame]

Hey,

is it possible that your floater-ring casts a bit too much of a shadow on it?

 

[sleepycloud122]

The floating plants are always on the move in the fish room but no, I don't think light is an issue, every other plant does well. Particularly the grisebachii tropica I thought it would be harder to keep than horemanii, but it seems to be not the case.