CactiGuide.com

Ive had this christmas cactus (Susan) under a year and she recently started flourishing with new growth. In the last few days her brightly colored healthy green leaves started turning rust colored and started falling off. Ive attatched pictures, it looks like evidence of fungus, maybe? It looks like evidence of fungus on the underside of the plant as well as the leaves She sits in a south-east facing window and i take her out into direct sunlight often but she is watered frequently. Her soil is currently moist. Is this a fungus? If not, what is it? Please help

Looks more like sun scorch to me. It's a forest cactus, should not be in direct sun, except perhaps very early in the morning or very late in the afternoon. Bright indirect light is best.