It may be that you've over-potted, which is choosing a container that is much larger than the last one - hard to say from your description.

The 'mushrooms' you are seeing are just the fruiting bodies of fungi that ware already in the bark. Don't be concerned, it just means conditions are right for the shrooms to fruit - no big deal.

If you're concerned about water retention, insert a wick into the drain hole & let it dangle below the pot after you water until the pot stops draining. Locating the drain hole near the edge (but still on the bottom) and tipping the pot at a 45* angle so the drain hole & wick are as low as possible makes a big difference in how much water your soil will hold. You could also just partially bury the container in a bed or garden. It only needs to be a couple of inches deep for the earth to 'pull' all the excess water from the soil.

It's better to repot/pot up when the plant is actively growing or just about to enter an active growth phase, so roots colonize the new soil mass quickly. You don't need to change to a different soil now, just be aware of how much water your soil DOES hold, and water when your plant needs it. I.e. when the soil feels dry at the drain hole; and use the tips you think are appropriate for you.

Al

Here is a link that might be useful: More about dealing with water-retentive soils

Bullet, I am in the desert. It's very dry, and I often go a lot longer than 10 days between watering.

It's fall, it's cool, and your plants are sleepy and not drinking a lot. If your soil is still moist at 10 days and you are watering once a week, you are probably over-watering.