So my fiddle leaf fig is a 3 ft tall bush and I water it about every 1 to 1.5 weeks when the soil is bone dry. I use a moisture meter for this so when it is under 4. It is planted in a 12 inch diameter pot. I mix a total of 6 cups of water with ~2 teaspoon of this liquid 3-1-2 NPK fertilizer. (About 1 teaspoon of fertilizer for every 2.5/3 cups of water). I do this for every watering right now! I got the fertilizer from Amazon! It’s the Botanicare CNS17 Grow. $30 for 128oz https://www.amazon.com/Botanicare-CNS17-Nutrient-Formula-1-Gallon/dp/B00IGFJXHC
Right now with my new growth, I’ve been seeing a lot of brown spots on the leaves due to edema, but they generally go away after the leaf has fully grown!