Duck - Swollen Inside Upper Mouth

My 3 week old duckling was outside in her pen when I noticed she couldn’t close her beak. Upon further inspection, the roof of her mouth in her upper beak is very swollen causing the beak to look tilted to the right and unable to fully close. Drinking water and eating is appears to be a bit of a challenge.

Inside towards the back upper mouth, I can see a black-rim spot about a centimeter in diameter. I’m wondering if she was stung or nibbled something sharp, but I have nothing concrete to go off of.

I gave her 1ml of children’s Benadryl in case it was a sting, but the swelling did not subside. After a few hours, I mixed a 250mg capsule powder Tetracycline in water (which I had on hand). I combined the 250mg capsule in 8ml’s of water and then gave her ~1ml with a syringe (some dribbled out her mouth). I’m not sure if this is the correct dosage because it was hard to find information online. I’m now giving her a full night rest to see how she responds by the AM. I will give her probiotics in the morning as well.

In the meantime, I’m posting some photos and would appreciate any feedback on what could be wrong or recommendations for how to better treat her so she can heal quickly.

Thank you to this amazing community for your help!

Hello and welcome to BYC! Glad you joined.
I see you started another thread in the ER Forum. Also consider asking what might be the problem in the Duck Forum.
Good luck and I hope she is improved in the morning.

Hello
Welcome to BYC!

@DobieLover has pointed you in the right direction...hope you get the advice you need and your duck is ok. Best wishes!

Hi and welcome to BYC We're so happy you've decided to join us

Welcome to BYC. Hopefully you have received some help with your duck.

Welcome to BYC. We’re so glad you joined! Good luck with your duckling!

Hello and welcome to BYC So happy you have joined our flock.

Best of luck with your girl

Good luck with your duck, and welcome to BYC!