I would agree with the other posters comment that this isn't really anything to do with the TV apart from the fact that it restricts a free flow of air across the carpet. Are you absolutely positive that there wasn't moisture on the carpet when you placed the TV in that position in the first place? or alternatively if the carpet had been wet cleaned at any time moisture could have crept along it under the stand, but apart from the possible reason mentioned by Peter (which should be easy to verify) I am certain that you can discount any technical aspects of TV as such as the reason for the problem. Another possibility might exist which you could have been totally unaware of, that being the concrete floor could have became damp at some point in time then dried out again, and so even although the floor may look dry now if the aforementioned happened it could have triggered the mould spores.

Could be moisture finding it's way down the aerial lead ...a common problem. For the sake of safety I would advise against using your TV or any electrical equipment around that area before it's been checked out.