That is a mess. The light duration should be OK, so on the light next question is, what is the spectrum (it looks OK in the photo, but do you know the Kelvin?) and the intensity. Have the light on a timer so it is only on the same 6-hour period each 24 hours, this is important for fish as well as plants.
Reduce your use of "fertilizers," they are clearly encouraging algae. Natural nutrients (fish being fed, water changes) may or may not be sufficient, but Flourish Comprehensive should be added once a week only, at the level recommended on the bottle (or less, but not more). Do not use the Excel, it is only adding to the problem, and it is dangerous to fish and plants and bacteria as it contains glutaraldehyde [research this to see how deadly this substance is].
Floating plants can help, both by shading the lower tank and by their incredible uptake of nutrients especially ammonia.