These flies, if there's nothing else wrong with them, can be salvaged. There's no need to strip the hook & re-tie the fly. I know an angler who used to do that & that's fine if you want to, but you don't have to.
How do you rejuvenate the hackle on your flies? Answer: with steam. Simply heat up some water in a tea kettle until it starts to steam & - with your hemostats holding your fly (be careful - remember, steam can hurt you) - pass the fly through the steam. Keep moving & rotating the fly through the steam. This will only take about 30 seconds at most.
When you do this you'll see the steam start to work almost immediately. With dry flies you'll see the hackles straighten out & go back to their original shape. Wet fly hackle will also straighten out, too. Any dirt, grease, or other nastiness on your hackle will / should come off in the steam. If not, the steam will loosen that garbage up enough for you to gently wipe it off the feather(s) with a soft cloth.
When you're done make sure you dry your flies thoroughly before you put them away, locked up in your box or fly wallet. Also make sure that as you let them dry that you place them in such a way that doesn't crush one side of the hackles you just straightened. A piece of foam to hook them in is ideal.
To show you the process, here's a photo of how I steam-clean the hackles of a dry fly:
It might sound like an infomercial to say, but you can breathe new life back into your flies in only a few seconds with the power of steam!!