GSP tips turning black

[gfcashmo]

Anyone ever seen this? If something has changed in the tank I would suspect it. Everything is consistent. Alll parameters are good. Lights are great

Any ideas? Seems the polyps are not coming out where black. I have some snails and hermits. I've has this gsp for a couple years.

 

[garygonzales]

i just think they are closing up a bit and maybe some algae is growing on it...