I have some Alpinia Zerumbet Variegata ginger all over my property and most of it (in partial sun) is thriving. However, one section in mostly full sun is struggling. Many leaves are yellow and have brown tips. I've tried increasing the watering, fertilizing, adding iron to no avail. The ginger in this area used to be healthy. The plants have been there about 10 years.

Any suggestions on how to fix or further diagnose my problem would be appreciated. I can email photos if that would be helpful.

I live in San Diego.