Plants can use light up to 10000K. The main difference is the higher the K
the more blue light it has. Also the higher the K
rating the brighter the light appears to the human eye. Many people like 10K bulbs with a pink rosette bulb to balance out the higher blue light with added red spectrum. Many people like the 6500-6700K range. It really is a matter of opinion what you think looks best. I use Geisemann bulbs 6000K Midday and the pink Aquaflora bulbs in my T5HO fixtures. I would suggest seeing what bulbs come with the fixture and if they are in the right K
range see how you like them. You can always replace them if needed or wanted.