The sword does appear to be dying, I have had this occur with a new plant. Make sure the crown is not buried (it is fine in the photo, but perhaps previously such as in the pot from the nursery/store it was buried). If the roots are fine, new leaves will emerge from the centre of the crown.
So at this stage, I wold not fuss too much. We all have the tendency with fish and plant problems to want to "do something" and this usually translates into dumping this or that in the tank as a cure-all. Patience is indeed a virtue.
Which brings me to the Excel issue. It is true that Excel will often (but not always) kill some algae, and brush algae seems susceptible. Seachem themselves state they are not sure why and they also do not recommend using Excel for this purpose since it may cause other issues. This is the answer taken from their FAQ in response to why Excel killed the algae:
A: This is a known side effect of Flourish Excel that may sometimes occur. It has been reported to us by other consumers, however it does not occur under all conditions therefore we do not promote it or sell it for that purpose.
Some plants will melt with Excel. It contains a chemical which if memory serves me someone found out to be formaldehyde [interestingly, my search just now at Seachem turned up no mention of what exactly is in Excel, but they do mention formaldehyde in an answer to why Excel killed Anacharis
]. In large doses it will kill fish. Seachem say Excel becomes inert after 24 hours, so as a carbon supplement it would have to be used daily to provide a continuous organic (supposedly) source of carbon. Given the chemical properties, this is not wise in my view.
Spot dosing algae using Excel full strength with an eyedropper--but out of the water--is said to kill the algae. I would not recommend pulling out all the plants for this, the effect of the chemicals might well kill the plant too.