Let it go, try not to do too much at once, it takes a few days for anything you do to have noticeable effects. Let the soil dry out between waterings, no real need to nute at this stage either. You can definitely tell they stretched pre HPS. get a fan on those plants, not too strong though, you dont want to blow them over. Everything will be fine if you take it slow and don't try to do anything too drastic.