Red creatures on my Betta's head

[Mithral]

I have a crisis with my Siamese fighting fish.
About three weeks ago, he developed a bump on his head.
I couldn't tell what it was, so I took him out and wiped the bump with a cotton bud. The scales came off and it looked as though he had a growth on his head. The scales grew back, but the bump remained.
Today, I looked at him and he seemed quite happy. The next time I looked at him, he had a bright red shape on the bump. The next time I looked, he had two spots and then the first one disappeared. Also, a small piece of red came off one of the creatures and floated away and was eaten by a guppy. My partner watched this too, so I know I'm not dreaming.
Can anyone help me to identify the problem?

[Mithral]

I have my Betta in with Guppies.
I keep the Guppies in outdoor ponds during Summer
and in aquariums during Winter.
We have leeches here and I have seen young leeches in the water,
but they are larger and never as red as these creatures.
They are bright red on a blue Betta.
I also have 2 bristlenose catfish and mystery snails as well as the guppies, but the Betta is the only one who has this problem.

I'm thinking that I may have to use a process of eliminaton as I am unable to find any information that can tell me what it is.

I think I will begin with a salt bath as leeches are very responsive to salt.
I don't want to lose my Betta.