I'm going to comment as i watch the marth ditto. All comments are directed at darko:
Okay, that ftilt approach in the begining was bound to fail. You need to use the "standard" or "good" approaches with marth, eg. his JC grab and fairs.
When you tried to edgeguard death on the first stock, you were standing too close to the ledge. None of your moves will sweetspot under the ledge if you stand too close. Especially Fsmash: It only hits a sweetspotting marth at the very tip. It's much easier to edgeguard if you stay within tipper range, so try to be more aware of where you're standing next time.
When you edgeguarded him the second time, you used dtilts when he was above you. That just seemed like a really bad idea, since you were again too close to the edge, and he was within attacking range of you. Of course, he died anyway, but he could have just faired you when returning to the stage instead of countering.
Ok, after death died: Wow, you guys need to use grabs more often, especially at close quarters. They will always hit before the Fsmash will, and they aren't half as punishable. That's why fsmash isn't a good approach/spammable while fairs and JC grabs are. You don't realize this because you're BOTH doing it, so there's no one to punish you for all the Fsmashing.
Ok, you're both at 3 stock now: Nice nice, a little better here! Good spot dodging, seems like you're both using more grabs all the sudden (which is good). In marth dittos, you have to be ready to DI -away- at all times. You didn't do this when death was Fthrowing you, and you especially hurt for it when he got that Fsmash off. ALWAYS DI AWAY FROM MARTH, it screws up practically everything in his arsenal: SHDF combos, Fthrow combos, ken combo, ect.
Alright you died because you didn't DI the fthrow. See? It's VERY VERY important to DI it, because wow, marth can really destroy himself in dittos with those Fthrows. Moving on: Okay, pretty much everything that happened on your next stock was self-explanatory. You spaced a little incorrectly trying to edgeguard him, and you missed the sweetspot while recovering. Oh well.
Last stock: You knocked him off with a pretty nice fsmash from below the platform, but you edgeguarded with B. Normally i wouldn't do that against marth, but it's not that much of a big deal since he died anyway.
Death's second to last stock: AGH, when death was at 32% you could have ended the stock RIGHT THERE with an Fsmash because he DIDN'T DI THE FTHROW PROPERLY. Always remember to do that when you can, especially when his back is to the ledge like that! It's a lot more effective than chain throwing, and remember, that simple combo is the reason you lost your second stock.
After that: Well, Death just seemed a little faster and more comfortable than you. No big deal, just work on your spacing and stuff and you'll get faster.
Ok, whew, i hoped that helped. Maybe i'll look at the second match later. If i sounded mean writing this, it was totally unintended.