Duckweed turning red

[JayT]

I recently upgraded my tank and got another set of LEDs and started CO2 for the first time.  The duck weed really responded to all of this - I've never seen duckweed with 2.5-3" roots!  I was doing a tank clean and noticed that the tips of some of the duck weed roots were reddish and the bottom of the leaves was also a red-purple colour.

I've kept duckweed for a long time and never noticed this before.  Is this common?

[wrm130]

Are you sure it's duckweed?  Pic?