It may be alittle transplant shock... Have your temps been high? If so you might want to shade them during the hottest part of your day for awhile until they perk back up. Like put plastic outdoor chairs over them. But I do realize you have 20 of them so that would be rough. Keep them well watered... Did you give them any granular fertilizer? I just did that to my starting the second year double KO's and they did not like it very much at al herel. I do not fertilze first year roses at all...

I have an iceberg that is doing this also. It's so heavy with roses that it's almost touching the ground. I am going to try the staking. Wish me luck. I think if I pruned it back, it might not come back for a couple of years from what I've read...but believe me, this guy is getting pruned back pretty good this fall or next spring! Good luck with your knockouts!

A 15-gallon pot is likely to be 18" across & nearly as high. If concerned about water stains from a pot standing on deck or balcony, you might pick up pot feet as an alternative to a wheeled dolley. They fit under the bottom rim to raise the pot, run a couple of dollars each & you'd need four for a pot that size. Usually found with the pots outside, as they also keep a pot from freezing to a bottom surface & cracking. Often use them & just slide a saucer beneath for water to drain to which can be emptied & removed in between waterings. Might consider using a few inches of mulch atop the soil to keep it cooler & delay moisture evaporation (kept from touching the stems) & pine straw for that is fine. Also keeps soil from splashing out in watering or rain. The potting mix you used contains slow-release fertilizer, but as others have noted, you'll need quick-release fertilizer for pots as well. The rule of thumb is "weakly, weekly" meaning fertilizer diluted in water at 1/4 the concentration on the bottle for monthly feeding, given weekly by pouring on soil already moist. Some of the fertilizers are very salty & can build up a residue on top of the soil & interior of the pot. Prefer fish emulsion myself. What a romantic gesture from your boyfriend! Sounds like he's a keeper, just like your rose... Here is a link that might be useful: General soil capacity pot sizes

I'm not sure what your zone is in northern VA, but I doubt you will need to winter protect. I don't have winter protection issues with my Knockouts here in zone 6b but I'd like to address pruning. I left mine alone for 3 seasons but now regret not pruning last spring as they only now bloom at the top and are taller than I wanted for the space I planned for. This rose will also hold onto its leaves longer than most cold-hardy roses. Don't worry about that, they will fall on their own eventually. In fact, the cardinals love using it for cover when they come to visit my feeder. They seem to like it even more than the native shrubs around it! I suggest waiting until early spring, which is from Valentines Day until Easter here, and then thinning out some of the the inner twiggy growth and shortening the shrub by one third at the most. This rose gets such a complete coverage of leaves that the inner growth tends to die out for lack of sunshine. And like any other landscape shrub, the lower branches will die if they do not get enough sunlight. Think wider at the bottom than the top to shape it. I didn't appreciate the Knockout clan until I saw what great 'doers' they really are. It kept them from my shovel more than a few times. They really are the easiest roses to grow, so enjoy!