Your Den looks healthy.
I see a new growth by the tag and the canes do not look bad.
The yellow leaf looks like an older cane that just may be time to lose its leaves.
I started watering every other day at the same time I started a seedling heat mat.
That was last November.
So I really don't know which helped.
In the pic (Without my hand) the 2 canes in front have grown since November.
The other pic shows all the Arial roots that grew since the added heat and water.
You may not need to tweak your care too much.
Try watering more often (Like I said, mine loves water).
The next thing to try is a heat mat until warmer temps head your way.