Hmm... I suspect what you saw were Viceroy butterflies.
https://www.butterfliesandmoths.org/spec ... -archippus
They start make their first appearance shortly before the Monarchs arrive.
Monarchs that you'll see this time of the year shouldn't be unusually small since they would be the migrating butterflies. Later on in the season, you might occasionally come across small undernourished Monarchs that for some reason had metamorphosed without reaching full size.
They usually don't survive the rigors of migration, however.
Monarchs should be coming around any day though. I saw one the other day -- the usual ones and two earliest scouts that I see in late June-early July, but I usually don't see the main group arrive until closer to mid-July. But you may see them earlier where you are since you are probably closer to the main migration route along the river and also may intercept the Pennsylvania interior migration group.
I think the ones that come to my garden are mostly from the Delaware Bay-Cape May coastal migration route and take longer to come north.