Common thing with leggy or weak stemmed transplants so yes transplanting them deeper eliminates the problem. You can mound up the soil around them to help support the stem if it is too late to transplant them deeply.

There are essentially no vegetable crops that cannot be transplanted deep enough to provide good central stem support.

Dave

My collards just emerged a week or two ago and, as usual, they're headed straight up. Chard, on the other hand, is a notoriously floppy seedling for me. I plant them in a 3/4-filled cup to allow soil to get mounded around their stems after they sprout. This isn't an issue of not getting enough light. They both get loads.

Concur, you can plant them deeper to hold the heads up better. Hot soil also tends to make them grow more stem. Common for radishes planted before the soil cools off enough, but also affects cabbage, collords, cauliflower