Will My Leather Survive?

[i have crabs]

dont use phosban with toadstools in your tank they have bad reactions to the aluminum, use rowaphos or some other gfo

[Sparkfarmer]

Is Seachem's "phosGuard" ok? What is a gfo?

[Navarchus]

Seachem's "phosGuard" containing aluminum.
gfo= Granular FerricOxide

but they have been steady with Alk = 8 - 10 dkh, CA @ 380 - 420 PPM, S.G. = 1.024 -1.025 and PH around 8.3.

That's not steady! Try to keep your parameters fixed.

Regarding the leather it is most probably shedding to grow larger

[Sparkfarmer]

Noted. Thanks.