If revenue is down, or if you've lost a large customer, or if a new competitor has entered the market, let your team know. Your employees need to know about the health of your company or organization. And it's only when they have the full picture — the good news and the bad news — that they can rally together with you to brainstorm possible solutions.
Don't keep your team in the dark. Don't give them a false sense of the situation by sharing only good news. Keep them fully informed. They can handle the bad along with the good.
Most likely they have a sense of the bad already. Or, they'll hear it second-hand. You'll gain their respect when they hear the bad news directly from you.