This happens when the displayport adapter is passive, you need an active adapter. And why one of the TV's is using VGA? I would use cheap DVI-HDMI adapter, a HDMI-HDMI cable and a quality ACTIVE DisplayPort - DVI adapter and a second cheap DVI-HDMI adapter on it. DP-DVI adapters are more available and you can use them for monitor eyefinity later should you get bored of TV's.
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