Your eyes adjust to low light. Your plants can't. What reads as a "bright room" to you is often barely medium on a light meter.

Distance is everything

Light falls off with the square of distance. A plant three feet from a window gets a quarter of the light it would at the sill. That's why your monstera is leggy even though the room "feels bright."

Use the map

Fern's light map measures the actual lux in each corner, then tells you what can actually live there. It's usually less than you hoped.