Is your fixture a VHO
(very high output) fixture? In order to use VHO
bulbs you need a fixture/ballast that will drive them, otherwise they won't even fire. Unfortunately, if you have a regular/NO (normal output) fluorescent fixture, you can't simply crank it up to higher output by putting higher output bulbs in it. Your ballast is the determining factor in how much light your fixture will put out, not your bulbs. And IME, VHO
bulbs are usually (if not always) T-12 diameter.
If you do indeed have a VHO
fixture you should be able to find 10000K VHO
lamps at marinedepot.com which will work well for plants.