Deadlift very slow off the floor, form check

Hi, I’ve been training for about 9 months now, and reached about 76kg bodyweight (ss nlp + bridge 3.0). Deadlifts used to be my favourite lift during LP (5RM: 122.5kg) but after finishing it I decided to brush up on technique, and move from mixed grip to hook grip. Ever since my deadlift took a huge hit, and now having finished the bridge 3.0, I struggle even with lifting 115kg off the floor (I’ve also gained at least 3kg of bodyweight since that 5RM).

I practically feel the weight fly after I pass mid-shin level (lockout is always easy), and I usually fail about 1-2 cm off the floor. I also have a problem with back rounding, which can be seen.

Here is the video from today 3rd August, which is a 125kg single @9.5: 20190803_165644_001.mp4 - Google Drive
RPE is really hard to tell, because I think I could break off the floor for another 2 reps if I really had to, but with some more back rounding.

Here is just for reference, the video from 15th April which was 122.5kg x 5 reps, during NLP (I take >10 secs between reps, sorry for that) : 20190415_164406_Trim.mp4 - Google Drive

Basically, my deadlift feels miserably tough only off the floor, and my back rounds a bit.
I also need to take more than a few seconds (8-15 secs) between reps if I pull anything heavy.

What could I do technique-wise to improve this ? I don’t feel like assistance work specifically for off-the-floor weakness is necessary, considering my beginner-intermediate level.
Basically, right now I feel like I could deadlift a lot more than I am, since all my other lifts went up by at least 5-10%. Thanks for the help.

I am not qualified to coach you. So I actually won’t.

I think you might be overthinking your setup and sabotaging it. I did however think the technique and setup in the newer video was better than in the older (I wouldn’t spend so much time in an uncomfortable position not lifting the weight)
I would suggest watching this video on a simple setup and trying to stick to it and see if it fixes anything:

Looks pretty good, can’t see anything horribly wrong. Back rounding isn’t terrible either. Not a coach either but what I found helps me with back rounding is tucking my shoulders back which tightens my upper back and puts my whole body a tiny bit lower because the shoulders can’t actually move up when you are holding onto the bar.

As for the problem with the weight, if you are going from 1 set of 5 on deads to something like 5@6, 5@7 5@8x3 as per BBM I would expect to take a hit on 1RM. It certainly devastated me when I first tried it.

It’s hard to tell from the angle…looks like your shins are vertical shutting off your quads ( wich break the bar off the ground). Try setting the bar a little further away. Also setting your low back harder this will prob help your speed off the floor. Good luck !