Leaf yellowing with red spots

[heavensent]

Hello, so apparently I am on some bad luck streak :/
On the pictures you can see the orchid in question.
Background:
I bought it two months ago in full bloom. The flowers started looking limp a week after but the plant looked healthy. A few weeks forward two leaves yellowed within 5 days and dropped. The spikes got dry and I cut them of and inspected the roots. They seemed healthy but there was little of them for an orchid with two very branched stems. The deteriorating you see on the pictures happened in a span of four days + some of the roots somehow dried.
The plant came in smaller white pot and I kept it that way, watered about every 5 days. Zero fertilisation. I can also see that some “air” roots where cut.

Could it be a disease or was the plant badly produced? Any other ideas?