Hello CKLD,
I'm not sure how long your gliders have been on the BML. Just want to give you another perspective from my experience, when I first put my gliders on the BML, their stools became soft (not pickable but still has distinct shape) and more brown than black for about a week. After a week, they slowly became moree solid (pickable) and darker brown.
MAYBE, it's just a transition?