Mexi, wtf? I tell you to get some fast growing stems and you buy moss? LOL
Stop blaming your poor fish! They don't eat moss or hairgrass- I promise, they are not evil fishes! They'll pull it up, push it around and make a mess, but they will NOT eat it.
Id put money that you're still ODing excel and that's why your moss looks bad. Excel ODs are bad for algae, but it will also kill mosses (and Vals). High temps will also cause this stringy moss - moss doesn't like anything over 80, lower is better, but IME, this looks like excel OD. as long as some of the moss is still green it will grow back when you stop ODing. It does fine at regular doses- you just cant go over.