Japanese Hairgrass leaves turned brown

[blink_willie]

My Japanese Hairgrass is growing well and spreading fast...but I see some brown/yellow leaves here and there.For some,it's just brown at the tip and for others the whole leave is brown.Some of my other plants like my myriophyllum are yellowish too.What is causing this?

My setup is as follows
-96W of T5 lighting 8 hours per day
-Pressurized CO2 at 2-3 bps 24/7
-I dose fertilizer once a week,here's what I use
-http://www.easylife.nl/english/index.html?id=40

Is there anything I missed out,or doing wrong?

Thanks for reading.

[Shadow]

how big is your tank? tank dimension?

[blink_willie]

My tank dimensions are 49cm(L) X 35cm(H) X 33cm(W)

[Shadow]

Is this new hair grass from LFS, if so maybe the one that turn brown is emerse leaves

[blink_willie]

No,it is not.I bought it in submersed form.Definitely not normal hairgrass judging from the price and the way it curls.