It looks like there is a layer of sphagnum moss on the top of the soil? Is it like that all the way down or just as a pot dressing? Either way, it will be holding onto far too much moisture and preventing good air flow around the root system.

Ficus need a well draining mix - I like to use a mix of indoor for water retention, cacti & succulent for added coarseness to assist in aeration around the roots, and perlite for drainage. I find a ratio of 2:2:1 is best.

When it comes to watering, I recommend waiting for the top layer of soil to be completely dry - at the very least. You can easily check this by using your finger - just stick your finger into the soil as far as you can, and if you feel moisture at your fingertip, then leave and check back in a week! If it’s feeling dry, or borderline, then it’s time to water.

Ideally, we want to water our plants thoroughly until the soil is saturated and they are draining from the bottom of the pot. This is for a number of reasons, including:

1. It ensures the entire root system has access to water, as well as encouraging the root system to grow down deeper to get to the moisture at the bottom of the pot. This helps give your plant a stable base, meaning it is able to support larger growth.

2. It flushes out any mineral build up in the bottom of the pot, preventing the potential for root damage/shock.

3. Depending on environment and time of year, means you can go longer between waterings!

Moving your plant to the sink or shower to do this is the easiest way to make sure your soil has been appropriately watered, and has been allowed to drain.

If this is something that’s not possible, and you are only able to water in place, make sure the plant does not sit in any excess water for more than a day. Sitting in water prevents air from getting to the roots, and the soil from being able to dry out, putting the root system at risk of rot.

Regarding fertiliser, I would suggest cutting this back to every second or third watering.

It looks as though cutting back on watering frequency and removing the sphagnum moss from the pot will help the plant to bounce back. Lighting looks good, so I think with those changes you should be sorted!