An additional picture:

Your insects look more like true bug nymphs than like adult beetles.

Thank you! Does that mean that they're juvenile or "baby" beetles? I think they may be gone now, but I thought they were interesting looking and unsure what they were.

Maybe a species of Largus. Very young baby bugs--as they get older their wings start to form and these guys don't seem to have that. (Beetles are really different and go through a pupal stage like butterflies before they show any similarity to adult beetles, but true bugs like these just gradually change into adults as they mature.)