Just saying
Watt = is symbolized as a capital W
wt = is the typical abbreviation for weight
No one going to mention he is trying to grow three plants with a total (approx) 50 W of blurple? Sorry icon, thats never going to work well.
How big is the space? Can you give us a link to the 300 W panel you are purchasing?
Height and coverage are linked, the higher you place the light the larger the area of coverage, however you are dividing the same amount of photons (light) over the larger area, meaning that each square foot will receive less light overall.
Inversely drop the light down to reduce coverage and increase photon count.