Yellow leaves on a melastome usually get blamed on the wrong thing first. It's tempting to reach straight for fertilizer, but overwatering is the more common culprit by a wide margin, and treating a waterlogged plant with more feeding makes the problem worse, not better.
Start with the pattern, not just the color
Older, lower leaves yellowing while new growth stays green is often simple nitrogen deficiency, especially in a plant that's been in the same pot and soil for a long time without feeding — a straightforward fix with a balanced fertilizer. But yellowing that shows up across the whole plant, especially combined with leaves that feel soft or a soil surface that stays wet for days after watering, points toward root problems from overwatering rather than a nutrient issue.
Yellowing with green veins still visible — a pattern called interveinal chlorosis — usually signals a pH problem rather than a general nutrient shortage. Melastomataceae prefers acidic soil, and if the growing medium has drifted alkaline, often from hard tap water or the wrong fertilizer over time, the plant can't take up iron properly even if iron is technically present in the soil.
Working through it
Check the roots first if overwatering is a possibility — healthy melastome roots are firm and pale, while soft, dark, or mushy roots confirm rot and mean repotting into fresh, well-draining mix is the priority, not fertilizer. If roots look healthy and the soil pH is the likely issue, an acidifying fertilizer formulated for acid-loving plants, applied over a few feeding cycles, is more effective than trying to correct pH with a single treatment. And if it's genuinely just an old, underfed plant with otherwise healthy roots, a standard balanced feed on a regular schedule usually resolves it within a few weeks.