Anneke

Ease off first if the plant is otherwise firm. Unpot it if you get a musty smell from the soil or more leaves go, and look for dark mushy roots: trim those back and repot into a chunky fast-draining mix. No point disturbing it on four leaves alone.

You have diagnosed it. Soft yellow leaves plus soil still damp three days later plus an unchanged summer watering schedule is too much water for the amount of light, and it is the most common version of this by a long way.

In winter it gets less light, grows slowly and uses far less water. Let the soil dry most or all of the way through before watering, which in a lot of homes means watering several times less often than in July. Check the pot actually drains while you are at it.