I don't know anything about eggplants...I will give my opinion on the buddleia :-)
If it were mine I might give it a small cut back but nothing major. I grow one and have had it 6 years in soil I think contains nematodes and this is one of its best years. I think the variety is Bonnie. It has grown all over the place but I won't prune til spring.

Good luck with your plants.

Eggplant will live for a couple of years but basically it is an annual. It is also effected by nematodes.

I have learned three things about buddleias.

Their roots do get eaten by nematodes, but normally they do well in the ground for at least two years. They do better in pots as long as you water them correctly.

They must be deadheaded.

Finally, they do not like "wet feet." This would include very heavy soil, which normally isn't much of a problem in Florida.

I keep buying them because the butterflies love them, but I put them in pots and after a while I get tired of watering them and then they decline. I have also killed a few by over watering. Slowly but surely I am being cured of this plant. What I have found to be much more successful and similar in many ways are the porterweeds especially the Stachytarpheta frantzii....a very large purple porterweed that blooms continuously throughout the year here in Central Florida. It will die back to its roots if there is a hard freeze, but it comes back nicely afterwards.