Here are some Thai eggplants about 3 weeks from seed that we are growing in our tent at the store. The front two are in recirculating waterfarm buckets, the back were started in 3x3 rockwool blocks, now on top of 6x6 hugos. They are growing under a 145 watt full spectrum LED. I grew these out last year in soil and they produced pretty well for a few months, kicking out really mild, tender green eggplants=)
When growing eggplants hydroponically, they do well with ph around 6.0, and nutrient PPM between 1750-2450. So once they get going they can be fed pretty aggressively. They need a fair amount of nitrogen in these early stages so adding a nitrogen supplement will make a difference. I'm currently feeding them House and Garden's Aqua Flakes A&B, as well as their nitrogen boost product.