Sick toadstool

I'm not sure about the rotting part.   But the feeler extension part I can tell you that it is typical that the feelers may not extend for up to several days.  My leathers have done this but have always extended back out.

Going back to the rotting part.  The bases of the my leathers are a different color than the rest of the themselves and have a different look about them on the part where they are attached to the rock and or glass of the tank including the upper side that is not touching the rock or glass.  It could be that they are not really rotting. 

On the light part of it.  The 18 watts certainly isn't very much light but I have a leather or three in a tank that has about the same lighting.  They are doing well and have pretty good feeler extension.  They don't grow very fast but look healthy.  You could place the leather higher in the tank if you are concerned.   I hope this helps.

I agree with Jake. When I got my first toadstool, after a couple of days the base started to rot away, first I though something was eating it, but then my dealer told me that I had to turn it around for the first little while ( why I'm not sure) Anyways I had to cut off the rotting areas, and I cut about 4 pieces. Although 2 died the other 2 grew really nice. You could also try giving them a dip in a coral medication.

Cut from the perimeter of the head of the leather coral. 

If you think your leather is not gonna live.   I would just cut around the entire head of the coral.  This will get you the most amount of cuttings from it. 

If you think your leather is not going to die.  Then cut a chunk off, then you will have the cutting and mabey still have the original also.

You can cut your cuttings into more pieces if you want to.   Place each cutting over a crevice on a rock "feeler side away from the crevice" and attach it with a rubberband or by stitching or whatever your preference of attaching corals is.   I like to stitch leathers.  Each cutting will then grow a new stock and become a mini version of the coral that it was cut from. 

If the leather is large it is recommended to do the cuttings  outside of the tank because of summm thiinnggg that they can release.    I have cut from my small pancake size leathers inside of my 72 gal. tank without any problems.

      

I remember Jake demonstrating this techinque at a meeting.  He secures the cutting to the rock by twisting the bridal veil so as not to cover the whole cutting.  Then secures the bridal veil with a rubberband on the under side.

Leathers or sarcofyton(sp) corals Shed. when the grow they sluff off there outer layer- that may be why only the base/stalk looked like it was rotting. If it has a real glossy look to it then it was just shedding.