
with Sooby, more space is better, especially if you don't know the ultimate size of your daylilies. Some can be pretty tall, making large clumps, and some stay quite small, but until you see their full size - at the end of the summer you'll have a better idea - give them lots of room. Do you know the names of the daylilies you planted? If so, look them up in the Plant Database and it should tell you about how big they will get.
Iris also need full sun and after they have bloomed their foliage stays tall and upright, and they increase during the growing season so they would tend to shade and crowd your daylilies especially if you have small ones.
If you want to plant something between new daylily plants to make the bed look good until the daylilies fill in, plant some short annuals.