Strange luminous glow on macroaalgae

[Plunder]

I have some macroalgae and at night when the blue light is on I notice just on one or two tips of several planted ones start to glow bright red/magenta it's really pretty. But I have no clue as to what it might be. Does anyone have any thoughts? Here is a picture.

 

[littlefishy]

I can't tell from the pic, but when my red algae have a dying branch in flouresces under blue lights.

 

[Plunder]

I did notice this morning one of the branches glowing last night was white and stringy like it died. Maybe something is eating them.