HELP!! DENDROBIUM ROOT DIAGNOSIS!!!

[emipr]

Hi I'm a new orchid grower and i really need help!!. Ok, so about 3 weeks ago I got a Dendrobium from my grandfather. It had two canes with 2 leaf, an a big one without any leaves. I also notice a keiki growing at the base of one of the canes. One received I re-pottered in a pot of the same size with a mix of gravel, pebbles, clay and brand new orchid bark, I watered and fertilize it with a 20-20-20. In the 3 weeks I have only watered 3 times ( once every 7 days) and kept it in a roof balcony facing east, so it takes sun in the morning and plenty of indirect sunlight the rest of the day. I live in the carebbean so the temperature is never under 80F and the humidity is never under 75%, if the temperature get above 93 (like last week) i put it in my room, where the air conditioner keep the temperature close to 60F. The Orchid however doesn't seem to be reacting, It hasn't grow, or shown sihgs of new canes, leaves or roots, in fact one of the leaves got yellow and fell. So i got it out of the pot to check for root rotting, but I really can not distinguish if they are ok or rotten. And if they are ok, why hasn't it react? why it's loosing leaves? I'm really attach to it and don't wanna loose it. I'll provide fotos for your convenience.