Both "The Newb" and Imperial Wraith had good points, I'm just going to nit-pick you for abit.
I watched the peach match, the first one.
So in starting...Whats up with those starting up-airs?...You did well though with a few tilts but you charged a smash, which was easily seem so she avoided it. Don't make things so easily noticed. You came on strong but once again, you started charging a smash..which stopped your assualt and got you hit.
You seemed to be into your f-airs too much and not really trying to combo into a killing blow, you just wanted to combo..and against peach, you really need that early kill. Your edgeguarding on peach could use work but then, who's doesn't? A nair is a great way to stop her due to if she airdodges, she still gets hit. You did decent with your dash dancing but you tried sheilding her d-smash, happens to me all the time so its either best to lightshield or dash away.
You did manage to catch a turnip, but I shy away from this as usually its more trouble than its worth due to it limiting your game, and perhaps if you didn't catch it, you wouldn't have been hit.
The running up-b, as Imperial stated...What the heck? lol...why? you should have known it wasn't going to connect. and once again..you tried the up-b knowing it wasn't going to hit, are you trying to be flashy and show off or something?..you were doing fine till this.
You caught stitchface..and you made horrible use of it lol...and you up-bed again but this time you did it wisely at close range, getting a solid hit. But you simply watched her return, not putting up any effort to stop her. You took to the air and hit a few times..but then she countered and was vunerable..easy kill hit and you didn't punish...lol and later on..you up-bed again..for god knows what reason. You d-tilted twice then f-smashed..you weren't reaching her but you tried again anyway? But you redeemed yourself with a well placed up-b.
Once again, on her last stock, she counters and screams "please f-smash me" and you instead swipe her with a single f-air..take advantage of moments like that. And the charged up-smash wasn't bright..but watching her return and you walking away for no reason was priceless lol
You have the up-b-ing disease. It hurt you more than it helped, if you stop doing it so much, it may not be as severe. Besides a few minor mistakes and your up-bing, your marth is indeed solid and can hold its own well.