Q.My Curry Leaf Plant Has Yellow Leaves, What To Do?
I bought the plant in May. It’s in a big pot on my terrace (south-west) in the Loire valley France. It has grown and is about 25 cm but now the leaves are getting yellow at the bottom especially. What has happened? Thanks

Certified GKH Gardening Expert
It could be a compounding issue. Anytime there is moisture around, it is possible to see these symptoms. Regardless of the exact ID of the fungus, it is just that. Fungicides will take care of the issue. You can try any number of things, but make sure that it is a treatment against fungi. Many soaps aren't strong enough to kill them, and will make the soil alkaline. This will be no good. Sodium bicarbonate is not good for plants, either, but you can try spraying a very dilute amounts. I would recommend potassium bicarbonate instead. It is way less toxic to plants.
The best thing is to get a registered fungicide. This disease is very easy to kill, so it would be a shame to kill the plant with treatment.
This mix is easy to make and will take care of the issue, safely:
https://www.gardeningknowhow.com/garden-how-to/info/diy-bordeaux-fungicide.htm

Certified GKH Gardening Expert
I am seeing the very early signs of Downy Mildew. You will want to get a grasp on this before it spreads. Most fungicides will do the trick, as it is not a difficult disease to kill. It will destroy your tree if left without treatment, though.
Here is an article that will help:
https://www.gardeningknowhow.com/plant-problems/disease/downy-mildew.htm

Thanks a lot for the answer BushDoctor. The article says it's often a problem due to the cold and humid climate but we had a very warm summer.... Could I try some general treatment based on Bicarbonate and black soap?
Could it be something else if not dowry mildew?