Masdies have me stumped

[wuness]

I've been growing masdies for some time in my greenhouse in Zone 5 (w. Illinois) and I'm familiar with their general culture requirements. I've had spectacular success with Copper Angel, but not with the other 10-12 I've tried. I don't let them get too warm (they go into air conditioning in the summer), and I give them no more than 50 ppm every couple of weeks. I use a high quality sphagnum moss in 3" clay pots. They're not in strong light and I keep them moist with rain water (or 1:3 tap water to rainwater). I repot every year or so.

I'm repotting now and nearly all of my plants have just the core root fiber left while the velamen is rotted away. My first inclination would be to suggest that they're staying too wet but I thought this group liked it that way.

I know every situation is different, but does anybody have any ideas I could try? wuness