8h per day is good. Plants take advantage of light only for about that period. Algae take advantage of light 24x7. If you run the lights longer, you will encourage algae growth over plant growth. Ideally you want plants to outcompete algae for nutrients, an 8h light cycle promotes that.
Regarding light color, I have never had a lighting source consisting of different colors, but for optimal plant growths, you are shooting for a color temperature of about 6500K. At least where I live, that is difficult to achieve with LEDs. My LED lights are 5000K, which is as close as I could get. A regular 'warm' LED light, eg for a living room, will be around 3000K, which is quite a bit more yellow.
As for intensity, for most plants it's the more the better, unless you have very high intensity lighting like people use for high tech planted tanks. High tech planted means dosing of CO2, dosing of nutrients, and high intensity light. YYou need to carefully balance these things, especially how much nutrients you dose. Under these conditions you can grow pretty much any plant, and they will grow fast. Typically people do at least once a week pruning. It's not a typical route for cichlid tanks to go, where most people choose a low tech planted tank - no CO2, no nutrients, regular lighting. In my experience, you want to go one way or another, but nothing in-between. For example nutrients without CO2 has always caused nothing but trouble for me. Without dosing CO2, plant growth will be much slower. It's not unusual for them to sit for weeks without showing much growth. I certainly wouldn't expect for much to happen 2.5 weeks after planting. At that growth rate, they get plenty enough nutrients from fish waste. CO2 they will get from decaying debris in the tank. You don't want a planted tank to have squeaky clean gravel as substrate.
In a low tech planted tank you are somewhat limited in your plant choices. I had good luck with Java Fern, Valisneria, Cryptocoryne, Anubias, Bolbitis, and Amazon Sword Plants. Anubias, and to a lesser extend Bolbitis, prefer very low light levels. In too much light the leaves get overgrown with algae, which then blocks light completely and can kill the plant. Amazon Sword Plants are the only plants I do fertilize in a low tech planted tank. I use Jobe's plant food spikes, which I break in half and push into the substrate right by the plant's roots. These are not meant for aquarium use, so you get them in a regular plant store.
Regarding light levels, there should be some guidance on the net regarding Watts per Gallon for low tech vs high tech planted tanks for fluorescent light strips, which could then be translated to LEDs.
What plants other than the sword do you have?