Let me first say good job for not posting all videos that you win in. Losing is the most important part of getting better and recognizing what makes a person lose is very important for anyone interested in playing competitively.
First of all, just because you CAN B-stick your specials doesn't mean you HAVE to. Two of the three videos you started the match by immediately doing a B-sticked PK Fire and whiffed completely. I noticed you B-sticked a Psi magnet while near marth in the first video as well which was either a mistake or just a pointless move. There was simply no way that you were going to hit with it. B-sticking your PK Fires can be useful but only if you use it intelligently. It is a spacing tool as much as an attack and isn't meant to be spammed mindlessly. In the first video you also tried to use PK Freeze on marth at close range...just don't ever do that again. PK Freeze should never be used at close range and especially not against fast characters like Marth.
Next, you desperately need to work on your PK Thunder. There were multiple occasions where you made an attempt to use PK Thunder in the middle of the stage and Marth hit you before you even got close to pulling it off. If you're going to try to use PK Thunder as an attack while on the stage you absolutely cannot be predictable about it. Mindgames and spacing are the key here. Adjust your looping patterns. Space it so that you can hit yourself just as opponents are getting near to try to punish you. It's a very risky move to use this way, especially against fast sword characters like Marth. You missed a few really easy recoveries with PK Thunder as well. Spend some time practicing your angles so that you can reach the sweetspot of the ledge from anywhere off the stage. Just takes practice. I also noticed that used next to no edgeguarding. PK Thunder is great for edgeguarding. Just send it out and loop it around to hit the opponent as it approaches.
Now for what you did well. You made some very appropriate uses of airdodging. This is something that people tend to forget. You used Lucas's jabs well. You predicted your opponent for some good forward smash hits. You didn't spam up smash like noobs tend to with Lucas. If I had to make some suggestions on your ground game I'd say to use forward tilt and up tilt more and dash attack less. Short hopped nairs are great too. Lucas has really amazingly good jabs so keep using them.
I hope some of these suggestions can help. I'd also suggest going on youtube and watching some professional Melee videos and watching how they space moves. A lot of it transfers really well to Brawl. Great vids and keep playing!
