This will probably follow what others have mentioned. First thing to realize, is that a new tank is biologically unstable, so algae has a real advantage. However, not encouraging it is advisable, and that brings us to the light and additives mentioned.
Excel is likely killing the very bacteria you want to establish, along with the plants...the Vallisneria is probably toast. Excel is the chemical glutaraldehyde, which is used in hospitals to sterilize surgical instruments so that tells you how toxic it is. At recommended doses it usually kills Vallisneria, but if overdosed can kill everything...plants, fish (if they were present) and bacteria. I would do some major water changes to get rid of this.
If you get your plants growing, and have some fast growing species (floating pl;ants are ideal for this) you donot have to "cycle" and that is one less problem. Plant the tank, use a comprehensive fertilizer, and when the plants show signs of growth--floating plants really are best here--consider the first fish.
The light reduction may help now, but the other aspects have to be in sync.
