Your plant MUST have good bright light and even more importantly moving air! Very pretty dendrobium!

Also be careful watering. The den should almost dry out before watering again. I’d also remove that small yellowed leaf at the base of your plant. I assume the pot has plenty of drainage holes, I can’t tell from the picture. If it is placed snugly into a cache pot ( pot without holes), the plants roots can’t get air.

If it’s getting too much rain, the roots can rot quickly. I’d ease the plant out of its pot and check the roots. If it is wet, I’d lay several sheets of newspaper or paper towels on a table and let the plant laying on its side so it can dry out, put a small fan on it if possible. Losing the top leaves is not a good sign.

Orchids are air plants. The roots need water but must dry out. And what Sheila said.