Red Gracilaria turning black?

[foxngn]

Hi guys,

I thought all along if a macroalgae going to die, it will become translucent and then broken apart and die.
But I got a red gracilaria, whether by it's branches were turning black/dark, while the tip of it is still red.
<the one on the left in the picture >

Does this still a sign they are dying?

 

[Big G]

How's the macro doing?

 

[foxngn]

surprisingly , it still growing & become more reddish. But still cant find out why though it turn darken.

 

[TriggerFinger]

Not sure on the black but I can confirm that macro turns white as it dies.