Your problems with mold and mushrooms might more likely be indicative of a problem with the potting soil you're using. For a while here, used compost from mushroom growers was very popular in soil mixes and potting soils. at first, it sounded like a great idea, however I started to see a lot of problems with mycelium overgrowth, both in pots and in the beds where I used it for amendments. The soil was infested with something that resembled "dry-rot" and was almost impossible to wet.
One year, a large batch of bulk potting mix from a reputable soil yard almost killed everything I planted in it over the course of a growing season. You know something is really wrong when well-watered and regularly fed potted daylilies decline over the course of one season. By the time I figured out what had happened, it was too late for many of them. When I started repotting the survivors, the soil in the containers had a noticeable chlorine odor. When I asked the people at the soil yard about it, they admitted that a batch of mushroom compost from their supplier had been sterilized with bleach prior to use by the grower. (Apparently, mushrooms are not very picky about their growing conditions.)
That was in the early 90's, however I've noticed that bagged potting mixes have steadily declined in quality from the glory days of the 80's. Today, many landfill operations are using scrap wood in their recycling operations, and some of them seem to be using dyes to disguise incomplete composting. The result is a soil based on softwood which breaks down quickly to muck. One sign of impending problems is when the soil turns from black to brown after a couple of waterings. Another potential problem is hazardous chemical residues on the scrap wood they are feeding their chippers.
Check the labeling on some of the big brand name potting mixes, and you will often find a generic term such as "composted forest products" in the ingredient list. This usually indicates that scrap wood from a recycling operation was used. Also, because shipping is very expensive, you may also see terms such as, "regionally produced" on a product labeled with the name of a company located a great distance away. This generally indicates that the parent company is contracting with a local jobber/bagger, who is probably working from a very basic recipe. I bought a bag of one of these from a big box store once, and when I opened it, it didn't have that earthy smell I associate with compost, rather, it smelled exactly like the local landfill.
This may be a "California Problem", because when I've bought plants from Plant Delights Nursery and Yucca Do, they are growing in a very nice, coarse, bark-based soil mix.
