Coffee plants originate from high-humidity tropical environments. One of the reasons that a coffee plant’s leaves may be turning brown is that there isn’t enough humidity in the air and the leaves are simply drying out.
Thankfully, this can be solved by giving the plant a good misting every day or so. You can also help increase the humidity in a room with a humidifier or pebble tray.
Too much sun
Coffee plants prefer to live in bright indirect sunlight. Too much direct sun can burn their leaves. Browning leaves could be a sign that your plant would prefer a new spot in your home, preferably in a bright spot like an east window.
Coffee plants like moist soil, but not soggy soil. If water isn’t allowed to drain or dry out enough between waterings, your coffee plant may be at risk of root rot. Browning leaves are a sign that the plant’s soil is staying too moist. Allow 25% of the soil volume to dry before you water. If you’re concerned your plant has root rot, you can actually physically check them. Dark and slimy roots are a sign of root rot.