Feedback Request

The author of the book featured in Face-Lift 1435 (just below this post) would like feedback on the following revised query:

Dear Agent,
I am seeking representation for my contemporary young adult science fiction novel, Vitality Discovered. Complete at 99,000 words, this debut shares the mystery of hidden powers and difficult discoveries found in The Light Through the Leaves by Glendy Vanderah, and the exploration of rare genes and the importance of relationships in Alice Sabo’s Children of a Changed World series. [If Alice and Glendy have the same agent, and that's the agent to whom you're submitting your query, you can be confident she knows what you're talking about. Otherwise you might want to mention other people's books after you've finished discussing your own.] 
For centuries The Legacy viewed the powers of vitality through a lens of superiority and religious fervour. [Fervor if you're in the US.] They accumulated or eliminated those with powers until very few were born outside their fold. [No idea what you mean by they "accumulated" those with powers. Recruited? Kidnapped? Assimilated?] [Better to start with your heroes than your villains, IMO.]
Eighteen-year-old Emily knew nothing of these powers, but they were making her very sick. Her first sense of vitality was the feel of it. The feel of it flowing within and around her was wonderful, but it was also being drained from her. Inner sight blossomed when Justin, her sixteen-year-old brother miraculously healed himself. A whole new way to see the world was revealed to them, and also to their thirteen-year-old sister Kayla. The intricate network of vitality flowing within every living thing sparkled energetically. It was beautiful, and completely inexplicable. Emily and Kayla could store and give vitality. Justin could manipulate and heal with it. [This all seems pretty vague. You used a lot of your limited space explaining what vitality is, and I still don't know what it is.] [Also, you say the powers of vitality were making Emily very sick, yet almost everything in the paragraph is about how great vitality is.]
Playing with their powers was amazing at first… Until they discovered that healing could go very wrong, that emptying your pool of vitality meant death, and that a dangerous cult was hunting people like them. And when their mother came home, she unknowingly started stealing vitality from Emily and Kayla. Finally understanding the cause of Emily’s mysterious illness provided little comfort. Acute leukemia [Leukaemia if you're in Great Britain.] was killing their mother. Emily and Kayla strained to control their flows and donated vitality to help hold the cancer back. Justin struggled to heal it.
Two weeks into this desperate effort, enough progress was made for their mother to return home between chemotherapy sessions. Tired but very happy, the teens relaxed their focus and Kayla’s pool of vitality emptied overnight. Only the timely use of a defibrillator saved her. Clearly [in] over their heads already, it was about to get a lot worse. While Kayla was recovering, a leader from The Legacy came knocking.
Fifteen years abroad, mostly in Asia, helped me set the scene for several important chapters in this book. Now permanently resettled in Toronto, my wife and I enjoy travel and the theatre, and I try to stay young by playing old-guy recreational sports. [It's unlikely the agent cares about this.]
Thank you for your consideration.

Notes
That doesn't seem like much of an improvement. How about something like this:
When sixteen-year-old Justin Smith miraculously heals his own broken leg, he thinks he's somehow developed a super power. He wonders, could he also cure his mother's leukemia? And his sister Emily's extreme lethargy? He tries, but it soon becomes clear that giving vitality to others also drains his own. 
Turns out the power to give--and take--vitality runs in the family. Justin, Emily, their younger sister Kayla, and their mother all have it. Oh, and did I mention that there's this centuries-old religious cult called The Legacy, that hunts down and eliminates people with special powers? There is, and they've gotten wind of what's been happening in the Smith household.
P3: What's the plan to keep each other alive while also thwarting the Legacy? They do have a plan, right?