Weak seedling stems

Hi all. Wondering what I should do about the seedlings.

A few have nice strong stems, but a few a really weak. With wind or watering, they fall all the way over! :(

They are maybe as much as 2 weeks old right now. Unsure what to do to help them grow ATM. They are outside during the day. On windy days we're putting them in the greenhouse (it's shaded now by our tree, tho it's pure sun in the spring!) so they at least get some light... I'm putting supports in for the 3" plants too.

Ideas anyone?

(pics later I think - camera acting up)