Yes it does matter, to the fish more than the plants. None of these plant additives are welcomed by fish, and doing anything like this at the end of the day when fish "hope" to relax is causing trouble for them. Any additives, medications, etc, should always be added in the early part of the fish's day (being their "daylight" period when the tank lighting is on), never at the end or in darkness. This will stress the fish even more because of the darkness/rest.
Second, as Fishmanic mentioned, Excel is a highly toxic and dangerous chemical that should not be used in a tank with live fish. The fish may "live" through this, just as they may/will "live" through the dosing at night, but that does not mean they are not being seriously affected. They are. All substances added to the water in an aquarium get inside the fish by osmosis through the cells and at the gills, entering the bloodstream and into the internal organs. Excel contains glutaraldehyde which is a highly toxic disinfectant used to sterilize surgical instruments in hospitals, to give you some idea of its toxicity and potency. This does not belong in an aquarium.
There is more natural CO2 in the average aquarium than most aquarists realize, and except in high tech systems the plants will have sufficient. Just balance the light and other nutrients to match.
Flourish Iron is not needed, and this is also causing issues for fish and likely plants. Flourish Comprehensive Supplement is a balanced nutrient additive; i.e., the nutrients (like iron) are in the correct proportional balance with each other, and this is important because too much of some nutrients can cause plants to shut down assimilation of other nutrients. Iron is one of these; and from my own experience I know what too much iron can do for some plants, not to mention fish. Iron is a heavy metal, and most conditioners detoxify heavy metals for very good reasons so their addition for plants should be minimal and controlled.