Completely agreed about the light level. I found that Dendrobium at the very minimum needs medium light level. Also, don't blame yourself too much; I found that if you buy orchids from places like Lowes or Home Depot, the roots are probably not in the best shape. If I do buy from them, after flowering, I would definitely repot the orchids to make sure the roots are not rotting. Here's some information about Dendrobium orchid. It tells you about Dendrobium's requirements and some background information. But I do agree with others that it might not be worth your while to save it since it would take so long (years) to recover a plant from that condition. Just go out and buy some more!! Here is a link that might be useful: Dendrobium orchid

Hort, who are these professionals? You will be hard pressed to find them. I've been trying to grow things for 37 years and still plants cark it. That is why we need an orchid forum. Sometimes you will find in posts little hints that make a difference. Anyway, it all comes down to conditions, conditions, conditions. Your Wal-Mart Dendrobium is probably a hard-cane, i've got about thirty of them and not many people grow them around these parts because they are considered "Difficult" . As for the disease, your plant is just showing what happens when conditions do not suit. I had one that grew too big, thought i would trial it outside a glasshouse and put it in a sheltered position of the front porch, sheltered position, morning sun. It declined! Moved it to my shadehouse. It declined more and then died. Your plant has declined to such a point that perhaps you should discard it and start off with a new one. These are the "weeds" of Florida, Hawaii, Queensland, Australia. They like moderate humidity, warmth, even watering, though slightly less in winter and sunlight filtered by some like shade-cloth. How can i tell you how to grow them seeing my total orchid experience is here? That is the real problem with orchid growing, you have to do some research and follow that up with some interpretation in relating what you read to your growing place(s). Even then many you try will just die.

I know that you mentioned it is a NOID Den but do you know what section it is in? Or whether or not it is a hard or soft cane type? I am sure that will influence the watering instructions.

These warm growing Dendrobiums have no resale value here where you can grow lots of stuff in your backyard without worrying about heating. The Dendrobiums grown around these parts are the cooler growing Australian Native Dendrobiums (species and hybrids) and the nobile types. Tried Latouria types and failed. At the shows around these parts Latouria and the warm growing hard-cane types are as scarce as hen's teeth and the one that you do see are poor relations of those seen in warmer climates. Similar comments apply to Vanda. Seduced by going on a trip to warm, sunny Queensland where the warm growing hard-cane type replace Cymbidium as the main genera grown. Sunny is not a problem. heating a glasshouse to maintain 55-60F minimum is. As for speciality, Cattleyas, Sarcochilus, Tolumnia, and those cooler growing Australian Native Dens comprise the main bulk of the collection.