Paul J. Johnson of South Dakota State University states that most orchid growers “pamper” their plants.

Two symptoms of this are over-watering and over-fertilizing which can cause break down of potting medium.

In the case of orchids, the potting medium is not used as nutrition as with most plants but to help provide moisture in the artificial environments of the home, office, or greenhouse, as well as temporary support  while roots are growing.
The more decayed the medium, the less breathable it is for the orchids’ roots.

Interestingly, there is an insect that can be used as an indicator of poor orchid care, event through they are commonly considered pests.
Probably all orchid growers have at least some of this insect in their plant collection, namely, fungus gnats.

The common fungus gnats in the hobby orchid collection are small, long-legged, long-antennaed, delicate flies with dark bodies and one pair of dusky-grey to black wings. Gnats are simply small flies, most of which do not bite.

The entire life cycle for the fungus gnats is about one month. They are common around the orchid plants because their larvae are feeding on the fungi growing in potting media that is too moist or wet, is warm, and the media is decaying quickly.

In other words, it is the over watering and over fertilizing of your orchids that bring out the best in these fungus gnats!