Pogostemon Helferi ... melted!

[Silviu Man]

Just don't understand what could happen.
I have (already had) a pogostemon Helferi in my 100 liters tank. No problem until now. Three week ago it start to melt down. The only chnage made in fert plan was replacement of Khalium-Potasium with Profito. There is no other change made in the tank. These are the pics, first from 1st of July and second right now:

Up in the attic I have the nano with Pogostemon Helferi plantated in the same time. And here it is :

So, it cannot be the temperature or other environmental conditions. Then ... what can be the reason why I've lost the first one?! Maybe somebody else faced same situation ... and can explain!

 

[zozo]

Maybe somebody else faced same situation ... and can explain!

I did, over and over again, but sorry can't explain.. It had everything i could think off, Co2, enough light and ferts.. Some say it thrives best in hard water, that i do not have. But looking further, others disproved the hard water theory with growing in soft water. Beats me what it is, one of those plants that maybe dislikes my face, looking at it and scared to death.. Dunno.. Likely there is an explaination, likely more than 1, but there are so many different parameters that could have influence, i don't even have a guess where to begin. I gave up on it and never bought it again. Hygrophila pinnatifida is another one i seem to stupid to get my head around it and make it grow, till now always failed in both ways, submersed as wel as emersed.

 

[Silviu Man]

I've notice that the death of the plants is related with the strains that not grow anymore and becomes thick. I don't know if my orbervation is right but I will try to trim it and replant.
Regarding the hardness of the water, I have same GH in both tanks, so ... I don't think this is a reason why it melts.