Ok so I'm watching your Marth ditto (cause they are my personal favorite. lol )
At the beginning of the match you get a grab and do a forward throw but you mess up. Just take your time. In a Marth ditto, you can do forward throw, forward throw, to up throw to up tilt **** from 0 percent. This is an ideal setup because you can use mindgames and trick your foe to double jump and rack up damage with Marth's uairs and other aerials to keep them in the air. You were also doing a lot of full jumping at random times. I'm not sure how long you have been playing Marth but just try and get his short hop under your belt.
Nice uptilt pressure though. I must say your edge guarding isn't terrible. Its not the best yet but you have an idea how it works. But you can take it much further. Try and get into the habit of wave dashing to the edge as well. When you grab the edge don't forget to renew your invulnerable frames by letting of the edge and grabbing it again. Ledge hop dairs are also an ideal edge guarding tool worth learning. As for off stage edge guarding, you can run of the level and swat your foe with a fair and Up B back. Or, for the sake of mind games, run off the level and when you get close you your foe Up B back to the edge. This trick can make your foe fall a little too low and make them activate their recovery a little later then usual.
You're overall speed with Marth isn't fast just yet. Get into the habit of dashing away after SHFFL aerials that either miss the target or hit their shield. For instance, let's say you do a SHFFL fair that hits a shield. After you have canceled it, you can dash forward to get behind your foe, turn around and grab. That's how awesome that trick is. Master it. Dashing away after your SHFFLs will make your Marth much more sexier.
Your DI and spacing need a little work. Remember, when you are getting grabbed or hit by aerials, hold away. But when it comes to powerful hits, like Falcon's knee or Jiggs' rest, you want to DI up in order to survive. As for spacing, the goal with Marth it to hit with the tip. So when doing fairs, for example, you don't want to keep moving forward. To space properly simply jump, hold back on the analog stick, and flick the C stick forward. Holding back on the analog prevents Marth from moving forward as he is doing an aerial. This allows you to land tippers far more consistent.
Avoid using your double jump so much in the air. You can simply DI away from your foe and use your forward B back on the stage sometimes. Mix it up, you know? Don't be afraid to air dodge either. Finally, work on canceling those dairs. ^^;
Oher then that, you have a pretty ok Marth. Its not bad at all. I think you'll be a true Marth player very soon. Just keep practicing. I enjoyed watching all of your matches, very well played.
Keep it up. :-)