Holes in plastron, please help.

[Quinnie]

So, I've finished Quinn's course of antibiotics prescribed by the vet for his abscess, (which is now healed completely) and his mild RI (just light wheezing once in a while, vet sid the antibiotics would help this too, but it hasn't gone away and it's been 6 months) but three days ago I noticed a small dent in his shell and I didn't think much of it, since it wasn't soft, smelly, bloody nor having white stuff coming out of it. But today I noticed another small hole.

I will add a photo when I can but right now it's the middle of the night...

I'm pretty sure it is shell rot because I've checked similar posts on another tortoise forum and holes indicate shell rot.

I really don't know what to do at this point. He's having so many health issues and I don't know what's causing them.
I feed him daily, he always has clean water, he has a 6x4 ft cage outdoors with natural UVB and sun. I spot clean and I just completely redid the substrate about 1 week ago but he just seems so unhealthy. How is he getting so much bacteria to make him this ill.
I will take him to the vet, of course but this is really starting to upset me. I don't know what I'm doing wrong and why he's so sick.

 

[Quinnie]

I can't add a photo right now but here's a photo that is very similar to what he has. This is not my photo, it was from another forum. But if I need to delete it let me know.

 

[Yvonne G]

Those look like bite holes. We'll need to see the actual holes on YOUR turtle.

 

[Quinnie]

Those look like bite holes. We'll need to see the actual holes on YOUR turtle.

Ok, fair enough. Although the forum I found that photo on deduced that it was shell rot since the person didnt have any way for the tortoise to be bitten.
Either way, I can provide a photo of Quinn tomorrow . Thank you.

also, I am going to start him on topical chlorhexidine tomorrow just to be safe.

thank you!