Did you rinse the coir well and get all the salt out of it? Coir is tricky to water. Do use the skewer to determine if it needs water.

The dendrobium likes tight pots, so unless you know that the medium has deteriorated, you might want to reconsider repotting it. If you do decide to repot, put it in the smallest pot you can that will accommodate the roots. And don't use fertilizer with high nitrogen. I use fine bark on my dendrobiums because the roots are fine. Medium bark would also be acceptible.