Hi and welcome!
You picked a challenging Dendrobium to grow.
However it keeps brownish canes. See the photo link.
dendrobium trigonopus - Google Search
From "The Dendrobiums" by Howard Wood:
Lovely, but difficult despite robust appearance. Restricted to a small Himalayan area at 1800 m (6000 ft) adapted to water deprivation but lives in monsoonal areas with heavy rain in growth season.
From "Dendrobium and its Relatives" by Lavarack, Harris, & Stocker:
Small epiphyte (grows on trees) in montane forests. In cultivation, this species requires intermediate temperatures, high humidity, & a dry resting period in winter, although water should not be entirely withheld. It should be given bright light and well drained potting mix or mounted on a slab.
That is what the experts say.
Here is my limited experience with the Formosae types. I'm in zone 7b which would be considered too warm for this Den outside (I grow in a shadehouse in summer).
My suggestion to you is to pull it out of the pot and rinse the roots. Check them for firmness and growth. Depending on where you grow will determine how to pot. These guys like early morning cool fog mist (think mountain forests where it rains cool every day around noon). IF you grow like this, mount the plant on a cork slab or a thick piece of bark that has grooves for the roots to attach. Make sure you attach the roots firmly to the mount so they can easily attach. Loose is not good. I use plastic zip ties and some cocofibers to hold humidity.
If you grow in pots these must be well drained. My experience with Formosae is that they don't want to have wet feet all day. Early mist is fine but they want to have lots of light and high mountain forest humidity NOT monsoon hot wet.
This one is difficult to grow so good luck. My guess is yours needs more cool light w/humidity. You're probably letting it dry too much.
IOSPE PHOTOS
Dendroibium trigonopus not growing
) and it grows under florescent, outside like you said, is too hot. I am positive on the idea of mounting it rather and have it hanging close to humidifier. I picked this dendrobium without double thinking - loved the smell of these very cute honey waxy flowers and thought it would do well in my place... But no, it's like other dendrobiums that send out a new growth right during or after blooming. This one has been sitting and sitting in the same position for over a month now. Well, I guess I will keep an eye on it and follow your advice on watering it. Sooner or later it will have to talk to me! 
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