Burr. Stefan Isler - Lava Flow - re-potting issues? (yellow leaves)

[Iwik]

Hi,

My husband gave me a Burr. Stefan Isler 3 years ago. The orchid was doing pretty well at the exception of a few black spots on the leave.

I thought it was time to re pot it and so I did. However, after just a few days (2-3) I began to see some tip of the leave turning yellow and more it goes the yellow take over the leaves. They aren't all this way but I'm worry that I did something wrong and will get worst.

Does someone know what I should do to avoid to lose my beautiful orchid?

Thank you for your precious time!