Help for eggplants that are turning yellow instead of purple

Q: I have a globe eggplant that was beautiful last year. Apparently, it is a perennial because it continues to grow (slightly elevated bed, facing south, close to the house, in Lakewood). My problem is that so many of the eggplants turn yellow. They are actually kind of a beautiful golden color, but they should be deep purple, almost black. The plant is laden with fruit, but they don’t seem to ripen. If I don’t pick them, the plant stops blossoming, so I try to pick the most ripe one