Slow up on the Excel. Easier to do that than to change the substrate (I love eco-complete) or remove the root tabs.
How many root tabs did you put down? How far apart? Some plants don't do well with Excel, and my guess is lots of them won't do well with an overdose of it. I'd stop it altogether for a couple of weeks and see if things bounce back.
Also, wisteria, anubias, ferns, and crypts are going to have little (if any) benefit from root tabs. They feed from the water column. I think pennywort is the same, though I might be wrong about that.
I usually recommend no ferts at all at the beginning of a new tank, unless you have enough experience to know what you'll need. Always best to see how the plants do, and add only the absolute minimum to get results you are happy with.
I blame spelling mistakes on my iPad. You should too!