Bachelor Buttons a hot mess

Oh man what trouble these have been. The first batch died after about 30 minutes in the sun as seedlings.

So the second set I meticulously set closer and closer to the curtains each day so that they'd get enough light to survive and prepare for outside. After a month and a half, they still wilt completely horizontal outside on a sunny day. Pictures I've seen of them have much shorter leaves, which I think is due to them wanting more sun. Such a bother for a full sun plant..

But anyway! I've had 2 plants shrivel up and die in the container already, getting the exact same treatment as the rest. And now a third, which was the tallest of them all has had its leaves flop, curl into pale greenielocks, and the bottom of the stem has turned nearly black and thin. I cut it down to 2-3" and might cut to the soil level, but don't have much hope.

What I'm worried about is the rest of them going the same way. I've tried drier, wetter, more sun, completely indoors. Nothing has revived them when they get like that. Is there any sign of something in particular here?

The bottom of the stem turning black and thin sounds like damping off, which is a common fungal problem with seedlings that generally occurs when you keep them too wet. That could very well be what killed your other plants too. Unfortunately once the base of the stem has shrunk down like that it's usually too late to save them.

Some general advice on getting things ready for outdoors...I'm not quite sure how you're acclimating them to outdoors after your gradual moving them closer to the window. Outdoor light is way more intense than any light they'll get indoors even right next to the window, so once you start moving them outdoors you need to start them somewhere shady and gradually work them up to more and more sun. There's also transplant shock, when you first plant seedlings outdoors their root systems are very small and not capable of keeping the plant from wilting when the sun beats down on it all day, so it can help to shade them for a bit after you've planted them if you have to plant things during the summer (it's better if you can get them planted out well before any hot weather hits so they have a chance to get their roots going first).

If you're finding this all to be way too much trouble, you might look into a technique called wintersowing. There's a forum here on it which you can access if you're a paid subscriber, or if not google wintersowing and you'll find lots of info. It's a technique that you can use to start things in place outdoors so you don't have to worry about adjusting them to higher light levels, etc as you will with things that you start indoors.

I thought of damping off, but I thought that only happened to seedlings. This one used to look perfectly healthy, and was about 7" tall. Can that still happen?

Trust me, I was ridiculous in how gradual I was bringing them out in the sun. The best I could get was keeping them outdoors all day, every day, but having to bring them in for a rest near the end of a sunny day, and they didn't harden off any more than that for over 2 weeks. Now, I just keep them inside the window because I don't have the energy to deal with monitoring them, and I'm afraid the heat wilting will weaken them enough for another one to succumb to whatever it is.

I expected to have blooms by now. I wish I was never given these seeds in the first place.