Epidendrum ibaguense new stems problem

[roland1120]

Hi guys, I hope you can help. We have an epidendrum ibaguense, it grows new stems but they dont look healthy. The first leaves are brown and dry, the newer leaves are green but brown spotty.
The humidity is about 50%, temperature is between 18-22 celsius.
It is in the window, but not directly in the sun and is close to the radiator.
What do you think?