Some kind of rot?
 

Hello,

I once again have an interesting case. I purchased this orchid in seemingly perfect state. However, shortly after buying it its flowers wilted… then leaves started yellowing, one by one from bottom to top until only this remained. I repotted it during that process and found a very nice root system. It was still dying of and I had no clue why so I took it out of the substrate again only to find rotten and dry roots. I HAVE to note that she recieved a very good care. There is almost no chance she was overwatered. Base of stem looks a bit off to me.

Could it be that ai purchased it sick? Did she die of old age? Her stem was quite long but it dried up and I removed it before taking pics.

This looks like collar rot. Have a look at the diseases section of the St. Augustine Orchid Society Web page.

What are your temperatures?

I have cca. 22 degrees celsius in my room, but I suppose it can get hotter these days because of large window.

Phals. enjoy high temperatures.