I can't help you with the brown spots near where the petiole (leaf stem) and the leaf blade converge. It's not typical of over-watering, under-watering, or a high level of soluble salts in the soil/ soil solution, which are the big 3 when it comes to dead areas at leaf tips and margins. If it shows up again in other leaves, we can revisit the issue and see if we can figure it out. The chlorosis (yellowing) on the leaf, more conspicuous near the base of the leaf, suggests the leaf might have been in the process of being shed for some reason undefinable from the info provided so far, which you did a very good job at providing.

The dark coloration on the top of the leaf petioles is normal. It is turning brown by the same mechanism that causes green bark to turn brown. The outer later of the periderm skin covering the leaf stem is virtually the same as young bark. As the stem thickens, the outer layer of the leaf skin (phellogen) dies and turns brown - the same morphology that generates bark. The reason it is conspicuous on the top part of the petiole is because it is on the outside of the curve. Cells on the inside of the curve (underside of the leaf petiole) are compressed, while the cells on top of the curve are stretched. Stretching causes tiny cracks which exposes cells to air that dries out and kills the cells in the area which is stressed and slightly cracked. If the leaves survives long enough, the underside might eventually turn brown as well; at any rate, the brown area will increase in tome as the leaf ages.

This is a link to a thread about Caring for Ficus in Containers Over the Long Term. It won't answer the question re the dark blotch-like necrotic areas on the leaf you pictured, but it will provide a lot of good information about what the Ficus genus likes. Watering habits and soil choice are key elements, as is attention to regular rootwork. I think it would be worth the read, given the concern I detect in your request for info. Let me know if you have other questions you think I might be able to answer.

Al

Thank you so much AI for your insightful response!

Glad to hear that the dark coloration on the top of the leaf petioles is normal. I was worried that some kind of bacteria is slowly spreading all over my plant, and that all the leaves will start dropping once the dark parts on the leaf petioles spread to the base of my leaves. I will monitor my plant in the coming weeks to see if this happens again and reach out to you if necessary.

By the way, I checked out your link and there is so much useful information over there. It is very timely as I plan on repotting this fiddle leaf fig. Really appreciate your help!!

Thanks for the kind words!

If you live in the USA, June is usually the best month for repotting, which is considerably more involved than potting up. You can pot up anytime, but potting up is a half measure which only partially alleviates the considerable stress associated with root congestion, and ensures the plant will remain limited in its ability to function until a pair of human hands gets into the middle of the root mass to correct the congestion and problem roots - roots that cross; grow straight up, down, or back toward the center of the root mass; and roots which are circling, girdling, or j-hooked.

As you might have gleaned from the link I provided, water/moisture management is a critical part of care regimens for plants in pots. You can easily monitor moisture levels deep in the pot by using a "tell". More here:

Using a 'tell'

Over-watering saps vitality and is one of the most common plant assassins, so learning to avoid it is worth the small effort. Plants make and store their own energy source – photosynthate - (sugar/glucose). Functioning roots need energy to drive their metabolic processes, and in order to get it, they use oxygen to burn (oxidize) their food. From this, we can see that terrestrial plants need plenty of air (oxygen) in the soil to drive root function. Many off-the-shelf soils hold too much water and not enough air to support the kind of root health most growers would like to see; and, a healthy root system is a prerequisite to a healthy plant.

Watering in small sips leads to avoid over-watering leads to a residual build-up of dissolved solids (salts) in the soil from tapwater and fertilizer solutions, which limits a plant's ability to absorb water – so watering in sips simply moves us to the other horn of a dilemma. It creates another problem that requires resolution. Better, would be to simply adopt a soil that drains well enough to allow watering to beyond the saturation point, so we're flushing the soil of accumulating dissolved solids whenever we water; this, w/o the plant being forced to pay a tax in the form of reduced vitality, due to prolong periods of soil saturation. Sometimes, though, that's not a course we can immediately steer, which makes controlling how often we water a very important factor.

In many cases, we can judge whether or not a planting needs watering by hefting the pot. This is especially true if the pot is made from light material, like plastic, but doesn't work (as) well when the pot is made from heavier material, like clay, or when the size/weight of the pot precludes grabbing it with one hand to judge its weight and gauge the need for water.

Fingers stuck an inch or two into the soil work ok for shallow pots, but not for deep pots. Deep pots might have 3 or more inches of soil that feels totally dry, while the lower several inches of the soil is 100% saturated. Obviously, the lack of oxygen in the root zone situation can wreak havoc with root health and cause the loss of a very notable measure of your plant's potential. Inexpensive watering meters don't even measure moisture levels, they measure electrical conductivity. Clean the tip and insert it into a cup of distilled water and witness the fact it reads 'DRY'.

One of the most reliable methods of checking a planting's need for water is using a 'tell'. You can use a bamboo skewer in a pinch, but a wooden dowel rod of about 5/16” (75-85mm) would work better. They usually come 48” (120cm) long and can usually be cut in half and serve as a pair. Sharpen all 4 ends in a pencil sharpener and slightly blunt the tip so it's about the diameter of the head on a straight pin. Push the wooden tell deep into the soil. Don't worry, it won't harm the root system. If the plant is quite root-bound, you might need to try several places until you find one where you can push it all the way to the pot's bottom. Leave it a few seconds, then withdraw it and inspect the tip for moisture. For most plantings, withhold water until the tell comes out dry or nearly so. If you see signs of wilting, adjust the interval between waterings so drought stress isn't a recurring issue.

Al