#1 -- Time for adjustment; Even moving it from one place to another in the same tank can upset a leather.
#2 -- Moderate lighting.
#3 -- Enough water movement to keep detritus from settling on it and to allow for easy shedding when it chooses to shed.
I've read several places that yellow leathers are particularly sensitive and don't like being touched.  A couple of the places suggested the oils in our skin irritate yellow leathers more so than other varieties of leathers.  To be honest, I've yet to see a healthy looking yellow leather in any of the LFS around where I live.  If I had, we'd have one for sure, as my wife loves the way they look.