"Sick" dendrobium, please help!
 

Hello, I am new in the orchid world and my dendrobium is dying, I think. The leaves have been turning yellow and falling off. It is a "liberty white" and it's in a plastic orchid container with coconut husk and a pinch of sphagnum moss on top. My mom keeps watering it when it's dry so I moved it to my windowsill. I really want to save it!

Attached a photo.

what is your grow zone? where do you put this plant =east window, south, weast?
I put my Den. Liberty White in a bright shaded south facing window...its watered every other day ...its in a dendrobium media mix...my humidity inside the apartment is 55% and my temperature is 80F...I have fans and humidifiers
This doesnt need winter rest...so my fertilizer and watering is constant(weekly weakly)
The fertilizer is Algoflash (a capful to a gallon) alternated with seaweed mix and wormtea mix...

Your plant is not dying. I see the green young tip of new leaf...it is normal to have the old leaves to yellow and wither...
dont mess with the roots because it will sulk and wont flower for a season...discover a watering and fertilizer regimen for both of you.

Looks like it's just losing the leaf on the old pseudobulb (PB). This is normal. This is the season for new growth so you should see a new growth coming from the taller PB soon. Keep doing what you are doing. If you start to lose leaves on the bigger PB I would repot it to take a look at the root condition.

My garden zone is 6. I have had it in a north window sill where my phal's do great, but recently moved it to the south facing window where it gets more sun. Another leaf on the biggest stalk is yellowing now. It was repotted back in january into coconut husk and a little spagnum moss and the roots where beautiful! I have a feeling my dry desert house is not humid enough for this plant.