I seriously doubt you damaged the vinyl with one of these clothing steamers unless you held it in one place for a while. You'd know it was happening because the edge will start to warp. Even so these warps will usually relax back into place once the heat is removed. I routinely use my Perfection steamer right down on the vinyl with no problems at all. That said, I do keep the LP spinning during the steam application. In fact, I think the steam is more effective this way. Otherwise you just give the record a warm shower. :-)
Do you vacuum after steaming? I find this to still be an essential step not only to lift the crud but also to dry the grooves. Moisture left behind will sound something like what you describe.
Also, I find that when steamed and cleaned correctly the surface noise and some fine scratches will sound a bit more pronounced. That's how you know you have all the crud off the surface and out of the grooves. But this also increases the detail retrieval and resolution so one may begin to find other problems in the playback chain.
