Bacopa Caroliniana Browning?

[AzzaM74]

My Bacopa had been growing well for the last few weeks but now has suddenly developed browning (as in pic).
I have a single T5 for 6.5 hours a day and daily dose TNC Carbon and TNC complete (3ml each day which I have just upped from 2.5ml per day).

Do I need to reduce my lighting further?

My other plants are showing similar browning.

The aquarium is 6 weeks old. Could this just be a maturitiy issue?

 

[kadoxu]

A bit more information about your system will probably allow us to help you.
Tank size, filtration, etc, would be good to know.

In a 6 week old tank, may just be diatoms...

 

[AzzaM74]

Tank is 180L with a 1400 LPH cannister filter.