So after more careful inspection I noticed I have all the props except for 1 whole complete prop with adapter. What was confusing me thinking I had 3.5 props was one was split in half lengthwise and I missed it on initial inspection. So I have definitely come to the conclusion it is a prop/adapter failure, moreover the adapter. I was using the STO adapters not the LP ones. I felt they worked really well and were always tight after everyflight. However in one previous recent flight I do remember taking off the prop and it being a bit loose. I just thought I myself may have forgotten to tighten it so since then I explicitly told myself to make sure they are all tight. I think over time taking them on and off they have become easier to loosen.
This has to be it cause the whole prop is missing with the adapter piece that goes on prop. I think having more stress as in weight from extra batteries may not help either how fast it loosened (the motors spinning faster/working harder in accel and braking), but still a prop failure. I will order now the Lynh Phan adapters and use them explicitly. I would NOT recommend the STO adapters to anyone now, because I know I made sure the adapters were tight before take off.