In the photos, the yellowing leaves are older growth, which appear to be undergoing a normal process of senescence. This is the gradual aging and then shedding of foliage as new growth replaces it. How quickly this happens can depend on the time of year as well as the relative speed of plant growth overall. Rapidly-growing plants can cycle-through old leaves faster than slower growers.

Leaves also have limited ability to adjust to changes in environmental conditions (light, temperature, and humidity levels) so plants may shed younger growth as well during an acclimation period, such as after being brought home from a greenhouse or after being brought indoors from spending the summer outside. Plants may have to regrow new foliage better suited to the changed environmental conditions after those moves.

If the light levels indoors are significantly lower than the plant received outdoors, more leaves may shed as we move into winter since the plant can't support all of its growth with the light energy it can collect. Indoor light levels are hard for human eyes to judge fairly since our eyes adjust to brightness differences very easily; in general, indoor light is much dimmer than outdoor light, even through a sunny window. If you prefer, you can supplement light for houseplants by using a grow light.

We do not see signs of pest or disease issues, so no treatment is necessary; spots appearing on senescing foliage are normal and not a concern. You can clip off the yellowing leaves if bothersome, but preferably let them fall on their own instead, since plants can recycle and re-absorb some of the leaf nutrients before letting it fall. Don't fertilize since growth will be limited over the winter and the nutrient boost won't be needed, and make sure its watering schedule allows the top inch or two of soil to dry before the next thorough watering. This avoids root stress from the soil being kept too wet, which can deprive roots of needed oxygen. (Stressed and dying roots can also trigger leaf yellowing, though often with young leaves in that case and to a greater extent than we see here.)

Miri