Is "these ones" correct?

No, saying “these ones” or “those ones” is NOT grammatically incorrect, though many people believe the opposite to be true. Those particular phrases are often frowned upon (more so in US English than British English) but have been around for centuries in both formal and informal writing (government, linguistic, theatrical, etc. documents/ plays/ books). Though many might proclaim them to be incorrect, many linguists do not agree. The idea of those phrases being incorrect is actually relatively new from what I understand, only emerging within the last century or less.

In The Oxford History of Classical Reception in English Literature, for example, one chapter's author uses the phrase “these ones.”

To conclude, phrases such as “these ones” are NOT incorrect, but are largely stigmatized and disliked (which also does not make them incorrect, however much those people might wish that they were). They might be a bit redundant, but redundancy also does not make them incorrect.

This article from Grammarphobia covers this question with a vast assortment of historical and modern examples by scholars and other authors.

I would say "are you talking about those?" or "are you talking about those earrings?". The latter has the benefit of specificity: it's clear what you're talking about.

As to whether or not you should avoid saying "those ones", it depends on your goals. If your goal is to mix with a high-class milieu, or project an educated image, then formal English is a good choice. If you want to fit in with average people, you might prefer to speak the same way they do. My preference is to speak as 'correctly' (as a usage prescriptivist would define correctness) as possible, but not to correct the usage of people around me, which they tend to find obnoxious. Of course, I'm a bit of an uptight jerk.