SocialistPete is giving some good info.

Like he said...Make sure there is plenty of bubbles. The more the better. Looking at the second video you posted, it looks like you've got a fair amount already but consider adding another airstone when you can. I've lost several plants due to root suffocation in DWC. Just ask Pete, he's told me countless times to get better airstones. So listen to him, he's good at DWC.

Your water level looks very low. Raise it until it's just touching the bottom of the pot. Once you have more (much more) roots then the waterline can drop, but until then keep it close to the netpot.

Is your pH in check? That plant, aside from being droopy, looks like it's got some health issues causing those cabbage looking leaves. Start with pH and we'll go from there.

keep it up.
Skeet.