Hi Lori5 - welcome to the forums!
There is no reason why you couldn't tag your emerging monarchs; however, as you suggested it is a bit early for your area and those critters probably aren't migratory.
If you plug in "Marietta, Ohio" into the handy little "How Far Is It?" tool at
you'll see that your latitude is 39:25:17N and if you refer to our "Peak Migration Dates" table at
you'll see that the etimated midpoint of the migration in your area is around the 22nd of September. You should therefore concentrate your tagging efforts around 14-26 September. Keep in mind that this is just a general guidline - if you observe dedicated monarch movement to the SW before these dates by all means tag away (and let us know what you're seeing in your area via the "Monarch Sightings" forum).
Hope this helps - Happy Tagging!