Bleaching/dying red algae..help!

[SteveConn]

Thanks for the input so far.
The LEDs were added to add more spectrum because the algae was dying.

The sump is fairly low flow. Water comes from the phosphate remover reactor. I can increase my flow.
I took filter socks off for a few days in hopes of improving nutrients, but still see a decline in the algae.
Could also remove the cheato for a bit and see what happens.