If these four experiences were 'first dates'/ solely implied sexual encounters, perhaps you simply need to spend some time getting to know your new friends, or maybe start with one and get to know her.
Opening your relationship goes against our societies and cultural dictations of how relationships 'should' be, I understand you and your wife are in agreement on opening your marriage, but maybe you are the kind of guy that takes his vows to heart so to speak. Perhaps you are influenced by what our society says we should and shouldn't do.
If 'opening' your marriage is what YOU really want, and IF intimacy is even truly wanted... than you may need to establish the relationship first.
Also, maybe just having a close relationship in addition to your wife may be all you need.
The most important thing is openness with communication with your wife. Remember... Deception destroys.