Mike,
I don't know what you mean by "medium filtered" light, but my educated guess is that it is not enough. Yuccas require lots of very bright indirect light at a minimum and really should have at least a couple of hours of direct sun each day.
When light is inadequate, growth slows so it is very easy to keep the soil too moist. I suspect root rot, particularly if you made the all to common mistake of repotting.
Contact me at wcreed@HorticulturalHelp for my article on complete Yucca cane care f you have further questions.
Will Creed
www.HorticulturalHelp.com
Will Creed
wcreed@HorticulturalHelp.comMy website