Sometimes it takes a while for the bulbs to warm up, if this is not the case than it could be the ballasts. This is little black box inside the fixture. When it is bad, what you are describing will happen. They can be replaced.
If you have blackened ends on one or more of the lamps (bulbs) it is usually a sign that the Ballast needs to be replaced. The way to check it is to remove all of the lamps and replace them with new ones being careful to make sure they are installed correctly. If they don't come up to the standard lumen level you can get a replacement ballast to match the one in the fixture.
There may be a fluorescent bulb connector from the right stick, so the electrical current does not go perfectly. Another possibility is it time to replace the lamp. My advice, change your CFL bulbs with LEDs, total cost and less maintenance. Many places which sells online LED lights have a very nice service. http://neeqe.com/store/index.php/