Green leather turning brown quickly

[rpkneumann]

Just purchased this wonderful green leather.
Resides on the bottom of my bioCube 32 tank.
Within 3 days it starts turning brown.
Help?
Alk 9.2 dKH
pH 7.96
Sal 35.0
Temp 78.9
Nitrate 10
Nitrite 0.1


before and ....

after (moved it for the picture)

 

[sp1187]

might be dyed. saw a beautiful pink/purple cabbage coral. supplier dyed it before shipping out to the lfs.