I believe it's Huernia Pilansii - Not a particularly easy plant to keep alive. Looks like one of the stems is cresting and forming a mohawk. I have a couple of these with one cresting alot like yours. I have had to pull these a couple of times out of the pot and seperate due to rot. If your plant isn't squishy at the bottom, some stem die off is normal - Stems of these plants naturally die back after 3 - 5 years. If it's young growth thats not doing well, it could be a number of things - light/water/fertilizer/medium etc. It's hard to tell. It does look a little overpotted - If you are worried about it, I would split it up into a couple different, little, & very well drained pots -

Hope this helps

T

The proper spelling is H. Pillansii - excuse me

T