If he replants outdoors yearly, does he use the same spots ? If so the soil may have become acidic or basic. You check soil pH if it’s a repeat grow area.
If it’s planted in like a field ,there may be other plants competing with or cooperating with the plants
If he replants outdoors yearly, does he use the same spots ? If so the soil may have become acidic or basic. You check soil pH if it’s a repeat grow area. If it’s planted in like a field ,there may be other plants competing with or cooperating with the plants