one of my spirulina culture, there is an unusual appearance. I'm trying to identify tiny circle structures but still can't. my culture colour is dark green not yellowish. it looks healthy but i have doubt about it is originated from spirulina or not. Culture's ph is about 9.2-9.5.

in the second image you can find spirulina from my other culture under microscope.

Could you please share your opinion and experience about it? Thank you in advance.