Hiya Tom...I'm gathering you're speaking of fluorescent tubes yes? Not CFLs?
Couple things to weigh...
What size tube, what wattage, and what is the volume of the space of your grow.
One negative aspect, that is, not an ideal thing, about fluorescent tubes is having a whole lot of light being discharged in directions where theres no plant to receive that light. Unless you make them vertical, they literally are wasting all the ambient light they give off. That in turn leads to inefficient use of electricity and light.
CFLs, (compact fluorescents) are a much better application for starting off younglings with. The light is more focused, making better use of the electricity it takes to power them. Also, they are far easier to handle and orient as a grower sees fit.
A 2', 3' or 4' tube oriented horizontally isn't going to get as much light to a youngling as would a CFL does when dropped down right on top of it.
Speaking of right on top of it...the practice of putting fluorescents 1-2'' from a plant comes at a price...to the tune of too much radiated heat being absorbed by the leaves. The grower doesn't see it, but those lil young'ns are having to expend and divert energy keeping themselves cool.
The ambient room temperature is not the same as the temperature of the leaves when a light is that close. To the tune of the surface temp of the leaves can easily be 8-12+ degrees higher than the temp of the air around them. Leaves absorb both radiated heat as well the heat of the waves of light. Thats a double-whammy.
3'' is as close as a CFL or tube should be to a plant. If using CFLs, I recommend keeping the ballast of them oriented so that the heat they cast rises up without crossing the path of any leaves. On CFLs, where bulb meets ballast, is the hottest part of the light. Depending on the wattage, this can range from 135 F/57 C - 190F/87 C. Easily negated with air circulation or cooled air...all the same...too warm for any plant to be able to do much more than just hang on till things cool down.
About growing with a lower Kelvin temp (warmer is lower, cooler is higher)...yes, plants can be grown under warmer coolers...but awfully slow until the plant is ready to begin utilizing more of the warmer colors for specific stages of growth. Likewise, flowering can be done under cooler colors...that flip flop though is not preferred by either the plant or the grower.
During vegetative growth, plants are utilizing the cooler colors of the spectrum to achieve maximum growth. When flowering, the same is true for warmer colors.
If you're indoors, spending money on electricity...might as well do it with the color that yields the best result for what stage of growth a plant is in at any given time.
Mixing your colors, yes, thats okay and won't hurt anything....but the plants will naturally aim toward the cooler color for sake of thats where they're going to get the proper light for vegetative growth. So, why even bother with a warmer color until such time as the plant will switch over to utilizing it instead of a cooler color?
Kade...flowering with fluorescents does not ****. One just need be sure to have the right color, and ample lumens to get the job done. While growth won't be as plentiful as under HPS, it does not effect potency nor quality of flowering...just the size. The personal grower need not be concerned with weight as much as potency.
Until you've flowered with a 2100K CFL or tube...you'd not know just how nice the end result can be. There are more and more outstanding grows being realized under fluorescent lighting. Yes, the light is not as intense as MH or HPS...but also nowhere near as hot as those mini bread ovens become.
Using the proper light makes for achieving a state where a plant thrives...not merely survives.
