The adductors are also hip flexors. So, if the psoas (a hip flexor) isn't working properly they could be trying to pick up the slack as well. This could cause them to become overactive/tight/stiff.
As with the traditional thought of hip flexors, don't bother stretching them either though. This might even give you pain too. The tight/stiff hip flexors/adductors are a symptom of the psoas not working properly. You don't give a cancer patient caffeine because of their fatigue (symptom), you try to get rid of the tumor (cause / psoas).
Remember though, make sure you are only training that hip above 90 degrees of flexion. Get rid of anything that trains that leg where it isn't flexing all the way. For example, using the elliptical would be a horrible idea.
And take your time progressing. Often times just trying to hold the hip above 90 is a serious amount of work for most people.
Also, if you're barefoot, sitting in a full squat for 30 seconds or more can be a ton of work for most people as well. They'll often nearly fall backward. Remember that if you're holding a weight in front of you you're actually making the movement easier and taking some of the work the psoas should be doing out of the movement. This is my long way of saying working to where you can just sit in a toddler esque squat, barefoot with no weight, is often the way to go.
Hope this helps; keep us updated.