I've grown eggplant for decades, and they have always has color consistent with what is in grocery stores. However, at my new home, they are mostly brown instead of the rich, glossy purple (pic attached). They are also somewhat smaller than expected, but all including the pic are firm. Are you aware of any particular soil deficiency that might cause this?
Hi, under-size, off-color fruits are not uncommon on plants that have grown and produced well during the summer but are slowing down due to cooler weather and shorter days. If this has been the case all summer long we suspect your plants are stressed, possibly due to one or more factors, including insect feeding (e.g., flea beetle, lace bug, potato beetle), insufficient watering, crowded plants, low fertility, compacted soil, etc.
The deficiency of a single nutrient probably would not cause this problem but we suggest you have your soil tested this fall:
If organic matter content seems low, consider spreading compost over the garden. Keep the soil covered with a blanket shredded leaves or consider planting a fall/winter cover crop: