Tokis-Phoenix: I already removed everything that could possibly scratch as soon as I saw the mark. I'm hoping that's what it was. But I did a treatment anyway just in case. There are no other plecs and no one bullies him. I'll take your advice on the diet and those meds too, thanks...
AndyTaylor: "not to lecture..."....... but you feel the need to anyway, right?
I do use test kits, I just don't have one right now. Simple as that. No lecture needed.
This is my favourite..."I'm sure you know this or you wouldn't be posting here, just reiterating." So, basically, you're not offering any knew advice/experience at all and are just pointing out the rather obvious, correct?
ETA: Thanks to everyone who answered and offered help, it's very much appreciated.