@John, there's obv the OP MU advice, but here's just a few ideas about the ditto i felt like sharing :3
In the ditto I like to chase down a lot. I catch a lot of turnips, especially while recovering. Why waste time pulling when you can just catch theirs, you know? Also, this is going to sound awkward and unconventional, but fullhop fair ***** in the ditto. It allows you to change heights in an irregular manner to the ditto, and you can use to to eat peaches double jump because it hits high enough.
dropping fair is great, if you get caught by it a lot try challenging with fullhop or high float nair. The matchup is about space control so consider where turnips play a part there and make sure you use them. Try to keep them on the positioning disadvantage and just get simple 14 damage hits.
@Kyle: Watching you vs tai. Here's just a few things I'm noticing:
Make sure you're di-ing the fthrow correctly, being down and out. I think you ate a few unfortunate fsmashes for that. If you can avoid the tipper, marth really can't place a kill move on you, and you can **** him from the neutral. Secondly, you either did not dash attack under his aerials, or you did it in the most first grade setting possible (0:25 was kinda predictable). You need to condition marth with your dash attack, that move ***** him. Thirdly, you seemed to pull turnips at unfortunate times. Not the worst thing, but it definitely put you in some situations you didn't want to be in. Get marth above you and challenge him from below with nair. Also, consider airdodging while recovering a bit more. On top of that, I keep seeing you throw out a lot of jabs. Those aren't too helpful in this matchup, if you're in a situation where marth can grab you, your princess hands won't save you, while a dsmash might.
Just a couple thoughts :3 good luck next time.