I will assume the light to be sufficient (LED is confusing to me to begin with) as far as spectrum (7500K is a tad high, but should be workable) and intensity, so reducing the "day" period may help. I found that having my tank lighting on for seven hours each 24-hour period was the longest without having algae increasing. Floating plants also help as they use more nutrients faster, and shade the lower area. Use a timer for consistency, and limit any non-day lighting, by which I mean the dusk/dawn lower light level. Plants cannot use this but algae can.
As for the fertilizer, the list of nutrients given on their website does leave out some important ones, and includes nitrogen and phosphate which are both unnecessary. I would look at something like Seachem's Flourish Comprehensive Supplement for the Planted Aquarium, Brightwell Aquatics' FlorinMulti, or another UK product I can't remember the name of but you are in the USA anyway.