What's up with my Dracaena??

[irThumper]

[EDIT: Dieffenbachia! Sorry for mix up!] Ok, I've never kept these before so don't know if this is normal, or if it means I'm over or under watering, or what. Can anyone fill me in? The leaves are usually green and white, but the last few days I've noticed a lot of yellowing... normal die off or...???

Will get some pics up in a bit.

Normal green and white...



Turning yellow and losing green color...



This plant is in a 4" plastic pot with drain holes. I just misted before I took the pics as the moss looked dry. I give them an actual watering once a week, but I've been misting a lot more lately to keep the humidity up for the PTF in residence. (10 gal tank, so know this plant is too small for it already and will need to be potted up and moved to bigger digs).