Hello plant parents,

I am a newbie at caring for indoor plants...adulting is hard.

Important information:
I live in Phoenix AZ. Very dry/low humidity here. I have one window in the bedroom where my plants are, it is a north facing window.

I purchased three plants from a nursery when I was in California vacationing. I’ve had the plants for a month.

A couple weeks ago I purchased bigger pots and more soil. The pots have drain holes. The soil is something pretty cheap I grabbed from Walmart.

Two of the plants are low water, more hardy plants. I specifically asked the nursery for ones difficult to kill...the third I fell in love with...and was warned by the gardener it would be a challenge keeping it happy. I am including a screenshot of the notes I took regarding caring for the Shinestar. Or as she called it “Shining Star”...I am having a hard time finding info on this plant online.

The Problems:
All three of my plants now have gnats. I have placed shallow bowls of apple cider vinegar with poked plastic wrap next to them. The gnats aren’t interested.
There seems to be a white mold or fungus growing on the soil.
The Calathea is starting to have yellow leaves and brown edges. A new leaf is wilting severally.

Hoping you can help this amateur! :)