So I was hoping to move these guys outside soon in...

I've just gone through very low media temperatures, and plants don't like low temps I've found. Air temp is one thing, but don't forget media temp. If the media/pot is not warm/hot, they'll stop growing or even go into reverse (leaves get smaller as they tighten up with the cold). Unless you have to for space reasons, I'd keep them somewhere warm until it's warm/hot enough outside. Perhaps even use the sun during the day and bring them in at night when it's too cold. Media temp must be >20c for decent growth to continue in my experience. Really young plants love ~28c.

Anything below 14 Degrees C can kill your plants. Unless they are strains bred for the colder climate. You can always put them out in the day and bring them inside overnight, until you get steady night temps of around 14 Degrees C or above.