I am not an expert on using ferts, I generally dose less than what you're doing.
What is your lighting?
Why the excel if you're using co2? Algae control? Some plants don't do well with excel- you will see burning leaf tips, dropping leaves, etc.
In my non-professional opinion it looks like maybe too little light- too much fert dosing. Just a random guess though. Maybe one of the experts on here will chime in.
***edit*** maybe I misunderstood your post. It looks like your aren't injecting co2, that would cause all those symptoms. You could also help your plants alot with proper substrate. Large gravel usually doesnt work well.