So, my mom in law left me all of her plants while she travels abroad for the next month and told me her coffee plant has been looking a little sickly and she can’t figure out why. I know absolutely nothing about this plant, but thought I would try and help heal it for her if I can while she’s away. Does anyone know what could be causing the leafs to brown? The newer leafs on top are growing fast and healthy, and the soil feels good and doesn’t have any signs of rot or infection. It’s also not in any kind of harsh light or in a dark corner, and it’s in a place where the humidity is slightly higher than the rest of the house, but not a significant amount. I’ve had it for a week now, but I can’t seem to make the lower leafs happy.
What's the watering like? Does it keep happening to other leaves?
I believe she waters 1/2 cup every five days? She uses an app that tells her when to water things. It doesn’t appear to be spreading to other leafs, but it might be growing slowly onto the leafs that are already bothered. I just got it a week ago and haven’t noticed to rapid of a spread among the already infected leafs.
That could still be too much or too little depending on soil and air conditions. A quick Google says they like slightly moist soil. If it's soggy, that's too much water. If they dry out, that's too dry. (Too dry is easier to recover from, but from appearances, it's probably too much rather than too little water.)
If it had plenty of other growth, I'd say you could remove those leaves, but it's not really big enough for that.
I don't think it's actually an infection. The only other possibility would be unsuitable soil conditions. I assume at some point it was repotted with fresh fertilized potting mix, and wasn't over-fertilized, though that could also cause what you're seeing.
Just in general, the problem isn't actually the quantity of water. Too much/too frequent water leads to 2 main real instead though. Not enough air getting to the roots, or a fungal infection in the roots / soil. The latter is the bigger problem for plants because you solve it by letting things dry out, which usually kills the plant before the fungus.