Some time ago one of my cinnamon pied girls had a missing patch of feathers above her eye (not adjacent to the eye but a little above). It looked like if someone shaved her in that spot. Not large, maybe 5 mm by 3 mm. Then feathers grew in that spot and she now looks normal.
Now the second cinnamon pied girl is having something strange on her head (but it looks differently than on her sister). It looks like a small wound to me, with red bloody color (nothing deep though), and there is white fluffy feathers around (that usually are not seen, usually there are yellow head feathers there). I am posting a picture (not a very good one). She behaves as usual.
Is it molting or something to be concerned about? None of my other birds have anything like this on their head.

It doesn't look like molting, but she may have banged her head on something. Some of my birds have gotten small, temporary bald spots like this because they crashed head-first into a wall while they were flying. This can be dangerous, but if she's acting fine now it means that she doesn't have a serious head injury.

Another possibility is that another bird may have pulled a few of her head feathers out. This isn't a problem unless it continues.

I personally wouldn't have thought that it was moulting myself. I would be concerned that they may be doing it to one another, whether that be through aggression or even over-preening. Have you witnessed any bickering between them? If not that then I would be thinking an injury as tielfan has said. Do they spook at night at all? I've had cockatiels really bash themselves around during a night fright

Thank you ladies. No, this particular girl isnt hanging out with anybody who could over-preen her.
They have a night fright rather seldom. Not recently or at least im not aware of it.
I held her in a towel this morning to check how deep it was, but i couldnt tell... its just a mess of pin feathers now. Hope she is ok

You said before that she was acting OK, the pinfeathers prove that new feathers are coming in. It sounds like everything is fine.

That's good. Sounds like there's no longer a need to worry yourself