Sunburn from direct sun

What's happening

Prayer plants evolved under the dim, dappled shade of the forest understory and aren't built for harsh direct sun. When strong rays strike the leaves through a window they scorch the tissue and bleach out the red veins and patterning, leaving dry, faded, brown patches — usually worst on the leaves closest to the glass.

How to fix it

Move the plant back from the window or to a spot with bright, indirect light, or filter the harsh rays with a sheer curtain. Maranta keeps its richest red veining and pattern in gentle, indirect light. The scorched patches won't turn green again, so trim badly damaged leaves at the stem if you want a tidier look; new growth will come in healthy once it's out of the direct sun.

This is general guidance based on common symptoms; individual plants vary.