Thank you all for your replies, they are very much appreciated.
I am sad to say that my Silver Molly did not make it. This morning, she was the same as before, no change for better or worse. This early evening, she suddenly swam quickly across the tank (no other fish were around her to cause her to move) and she settled down on the gravel again on the other side of the tank (which was near my heater--water temp read 76 F at that time). I noticed her breathing (gill movement) was remarkably slow in comparison to what it normally was. Her chest also appeared swollen and I notice a slight yellow tinge where her pectoral fins joint to the body and also the same tinge on the edge of her gills (scales layed normal and the yellowing was not fuzzy or anything like a fungus). Resting on the gravel, she a few times slipped/fell sideways, but quickly righted herself again. Within an hour, it was over, she passed away. I removed her from the tank, and noticed her chest underside felt "squishy"--I'm not sure if that is normal, considering she seemed suddenly swollen there, I think probably not. I redid water test with a 5 test strip kit, all parameter showed normal ranges. I have a friend that is an exotic veterinarian and I am going to have her look at the body and I'm also giving her a sample of the water for a lab to test to make sure things really are the way they should be.
A concern I have is that test to the lab may take a while. All my other fish appear fine and happy, but I am concerns since the Silver was with them all. I am particularly worried about my other two Mollys (the male Black and Female Dalmation) since they had quite a bit of contact with the Silver. Like I said, they appear fine, but if anyone thinks there might be a concern, any advise would be appreciated. If there is a concern for my other fish, I would like to fix it before they start getting sick too.
Thanks in advance!