Weak Duckling need advice ASAP

[Remedy]

I was able to successfully hatch my first three Call ducks 7 days ago. I’ve hatched crested and runners before but no Call Ducks. One duckling has a very hard time keeping up with her siblings, and they are already twice her size. She won’t pant but she will breath heavily, and lay still for a lot longer than her siblings. She’s scaring me bad.
When she does get up to move around to follow her siblings she’ll have to stop soon after and I can feel her little heart just racing.
I’ve given her B12, poultry nutria drench, electrolytes, and probiotics, and nothing is helping her. I have her on non medicated food which I’ve seen her eat. It’s duck starter grower.
I’m just at my wits end, I don’t want to lose this little one. Any help or advice is defiantly appreciated!
Her siblings still sleep with her and don’t leave her behind for very long so that seems promising? Right?

 

[chickens really]

Don't give it anymore electrolytes because that's hard on the heart. Have you tried wetting the feed to a soupy mix? Fresh water at all times to dunk their heads.

 

[Remedy]

Don't give it anymore electrolytes because that's hard on the heart. Have you tried wetting the feed to a soupy mix? Fresh water at all times to dunk their heads.

I stopped electrolytes three days ago, and have just being occasional go in her B12 when she seems really bad.
I keep the food right next to the water dish and even put food in the tray I have below the water so they end up mixing it themselves. :\ Thank you so much for replying!

 

[Remedy]

I stopped electrolytes three days ago, and have just being occasional go in her B12 when she seems really bad.
I keep the food right next to the water dish and even put food in the tray I have below the water so they end up mixing it themselves. :\ Thank you so much for replying!

I forgot to mention that she is slightly swayed legged. She’s walks kinda stiffly.