I have a large potted euphorbia that has really flourished in the 5-6 months I’ve had it, with the large pom-pom growth everywhere. It’s on a southern exposure balcony in southern CA Recently, it was moved from the east side of the balcony to the west side and brown areas are developing. I get sun all day. Should this be treated or just cut back? Thanks.
Most Euphorbias do well in full sun, but the move may have been to quick for your plant to adjust to the light condition change.
You can gradually increase the hours of full sun for the plant. Also the soil is likely drying more quickly in the full sun location. In warm hot weather you may need to even water twice a day.
I would move the plant to a partial sun location to help it adjust.
It does look like you have some loss to some parts of the plant. You will need to trim the dead plant material from the plant.
Here is a link with care information for this species of plant.