Hm, maybe you need to press harder down on the strings and/or tilt your fingers up a bit more so you're not muting any other strings, idk, maybe it could be the sound quality of the video, but that's just my first impression. I think you're playing was okay.
Meh, I'm a guitarist... 4-5ish years, bass guitar for around 3 years, drums for a year, piano for 5... among others ><
Also, maybe you could try strumming with your thumb and index/ormiddle finger together, etc, if you were using your index finger, you'd be making the "okay" sign, or the a-hole sign (however you see it o.o), just with the other three fingers curled. That's pretty much how I strum, when i strum up I sort of subconsciously move my thumb out a bit, strumming down my index/middle goes out a little, so the nail's always hitting the string. Imo it sounds better than just a thumb or a pick.
