My money's on phytotoxicity from the insecticidal soap. You may also be over-watering for all I can tell from here, but that usually manifests as drooping, yellowish leaves and leaf-drop, not blotches. A picture would be good, though.

I can't get my head around what you were doing with the foil, so I have no if that might also have an effect.

According to the University of Florida link below, these are the symptoms of soap-burn:
Symptoms on foliage include yellow or brown spotting, "burned" tips, and/or yellow or brown scorching on the leaf edges.

Sound like what you've got?

Some of the standard recommendations with Insecticidal Soap are not to spray in hot conditions, and not to spray on tender seedlings. Oops!

I probably just would have left the white-fly alone, but it sounds like you're setting up a new garden and may not have a background population of beneficial insects yet.

One gentler option is to give the leaves a high-pressure squirt every day for about a week to remove adults and also check leaves for larvae and remove by hand. Since you only had infestations on a few plants that had hardly any leaves that probably would have been do-able

Another soft option is to vacuum them off in the early morning (when its coolest and therefore they are slower moving). Empty the vac into a plastic bag and freeze it to kill the adults. Again, if only a few plants that wouldn't be a huge chore to do a few days in a row.

You can buy Encarsia wasps to control whitefly (often used in greenhouses), but honestly hardly worth it for a few seedlings and the blazing heat probably wouldn't help them either, especially if your garden is sparse and inhospitable.

Anyway, don't give up on your eggplants yet, unless you really need the space. They may recover from their shock and surprise you. And look on the bright side, the whitefly are gone ; )

Here is a link that might be useful: Info on using insecticidal soaps

ausbirch,

Thanks for the reply and information. What you said encouraged me; if it doesn't save them this time, I'll know better for next time.
To clarify, I read that aluminum foil under plants disrupts whiteflies' flight patterns and they leave. I don't know if that's folklore or what.
Also, I wonder if I even had a really bad whitefly infection at all because I never saw colonies of whiteflies under the leaves, just the tell-tale whiteflies flying around when leaves disturbed and silver steaking on some leaves.
I am trying out how I would manually removed eggs/larvae from tender leaves without hurting the leaves. That seems almost impossible. I like the vacuum idea. Sorry I don't have the capability at this time to upload of picture.
Thank you so much!

I am trying out how I would manually removed eggs/larvae from tender leaves without hurting the leaves.

By supporting the leaf in the palm of one hand and rubbing the thumb of your other hand over the leaf surface to squash the larvae onto the leaf surface. Wouldn't kill them all but might thin the herd. They're sooo tiny you'd never pick them off one by one! A more usual option is to remove the most heavily infested leaves but since you said your seedlings only had 4-6 leaves each that's a bit drastic! ; )

Sounds like the infestation was light anyway. Hopefully you won't have to deal with them again.

Hope the little guys make it (the eggplants, not the white flies).

I wonder whether this would work for whitefly since it works for flea beetles, which are the main enemy of eggplants here:

A friend told me to try growing my eggplant seedlings on a raised area, like a deck or a balcony, until they got big enough to withstand the challenge of the flea beetles. Apparently flea beetles don't fly much above ground level. It worked like a charm and I have beautiful healthy plants with nice big fruit this year for the first time in ages. I would think from your description of the problem that, aside from the whitefly, you may have been overwatering. But I don't know if that's possible in a desert climate!

By the way, I used silver mulch for my eggplant AND my squash for the same reason you use aluminum foil. Last year it seemed to work really well with my squash and helped me have a great crop, but this year the squash bugs seemed to find me anyway although I am still getting some nice zucchini.

And of course the balcony/deck technique won't work for you this year if your plants are already in the ground, but it might be worth trying next year.

Eggplant seems to be capable of recovering from a ragged state of looking beyond salvage. So give your guys a chance.

I suggest that you buy yourself a nice big piece of shade cloth, because of where you live. Many veggies that would normally grow in full sun do well in extreme heat if they are grown under shade cloth.

Just google either greenhouse supply or shade cloth to find a good deal on shade cloth. Look for the double knit kind that can be cut to any shape without hemming.

I had my eggplant under shade cloth up until a week ago. Now it's been moved out into full sun because it is bigger and tougher. My peppers seem to love heat, but they also like the dappled shade, so they are still under the shade cloth.