Ninae: what caused it? Did any of them have children? Did soemthing bad happen to them that could have drained their energy?
With age, for one thing the form deteriorates, which happens to everyone. The skin and eyes start to hold much waste and toxins and isn't as permeable for energy to shine through anymore, so someone becomes more dull-looking, compared to the sparking eyes, etc. that is seen more in youth. Also, a woman's body can become emasculated with age, which isn't flattering, and I think birth-control pills are part of it).
Everyone has to age, even the ones who make the most effort can't hold back age for more than 10-15 years, and eventually when they start to approach 50 they can't look like a young person any more. The only way to age as good as possible is to keep super-healthy and any kind of unhealthy lifestyle, and drugs and alcohol is dramatically unhealthy, can make your body fall apart before its time.
As for the energy-aspect, it also tends to go downhill, not always. There are some who mange to uphold their strong positive energy and joy of life with age, but most will become more burdened by life, many depressed about aging, so their personal energy will be less positive or high-consciousness and that's what will drain them of beautiful energy. Most of us are at our highest point when we come into this world and has been restored in the arms of God, and most are at their highest-consciousness as children (children generally have very positive energy). So when your energy becomes less postive and lower-consciousness you also lose your beauty.
Helena Christensen is a good example, she used to have an extremely high-consciousness energy, almost other-wordly, and it has dimmed over time. But when people are exposed to powerful spiritual, high-consciousness, or posivie energy they perceive it as very beautiful. And it is, only it exists more on the invisible levels and we can only vaguely sense it with our physical senses, but it's just about perceptible visually. She was definitely very spiritual, almost goddess-like looking, and it's not just down to the physical features, which we can see now that other-wordly energy is gone and without those powerful positive feelings of joy and love.
The voice can also transmit energy that way. Or higher-consciousness energy can be audiable and transmitted through the voice, especially if the throat-center is strong, and can give it a more beautiful sound and melodic tone (sound is all vibration). That's also how we perceive feelings through it. My mother used to have a very musical, angelic voice (some I've inherited that has gotten me out of some trouble). But, yes, I think your consciousness can be heard in your voice, like it can be seen in your face (we're all just an open book).