Fred is right, you just have to bury the bad with good. Since you've noticed that you're losing $$$ you may be more open than some to the idea that this is a marketing issue, and you'll need to spend some money on it.
The only way to guarantee someone leaves you a review is to pay them, so figure out how much to reward your real customers to leave real reviews and give them that as a discount or rebate after they leave the review. According to my Google friends, you aren't allowed to pay people to post Google reviews, but you can give people discounts on future services or a reward after they post a review. (I argued the difference, but the people I talked with just shrugged and said "that's the way it works.")
Stay away from paying a company to stack fake reviews. Suddenly going from 10 to 150 isn't believable, and you risk getting the Google death penalty, so take the slower route and reward your customers instead.
PS: We haven't systemetized a reward procedure, so have few reviews as well. We'll get on it one of these days.