Suppose I have domain working https like
https://www.example.com/ and my blog is working without https like
Is that wrong from SEO or Google point of view?
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Since 2014, Google has been giving websites available over HTTPS a slightly higher search engine ranking score. Given that your blog is only available over HTTP, it may appear lower in the results for some searches. However, Google isn't penalizing web site owners if other parts of their web sites aren't available over HTTPS but the main site is, at least as far as we know.
Thus, not using HTTPS for your blog will only affect the ranking for your blog and not that of your main web site.