Background: Critical thinking is one of the 21st Century competencies for students. While previous research acknowledges the potential of peer feedback to enhance critical thinking skills, particularly within computer-supported collaborative learning (CSCL) environments, there is limited understanding of which specific aspects of critical thinking are improved through peer feedback and how various components of critical thinking are interrelated within a CSCL environment in K-12 education contexts. Objectives: This study aims to investigate how peer feedback affects secondary school students' critical thinking skills within a computer-supported collaborative argumentation (CSCA) environment. It explores the specific aspects of critical thinking that were enhanced and examines the relationships among different critical thinking indicators using Epistemic Network Analysis (ENA) to provide a deep understanding of these skills' development before and after peer feedback. Methods: This study adopted a mixed-method approach. Qualitative content analysis was conducted to explore the effect of peer feedback on students' depth of critical thinking by adopting Newman's framework. Quantitative ethnographic method known as ENA was employed to analyse the co-occurrence patterns of critical thinking influenced by peer feedback. Results and Conclusions: This study found that peer feedback was effective in promoting students' critical thinking measured by Newman's framework (Justification, Ambiguities, Importance, Novelty, Relevance, Width of understanding, and Linking ideas, factors, and interpretation). However, the study noted a lack of improvement in the dimensions of Bringing Outside Knowledge/Experience to Bear on the Problem (O), Critical Assessment (C), and Practical Utility (P). Peer feedback significantly influenced the co-occurrence patterns of critical thinking. Before peer feedback, students' arguments were characterized by confusion and narrow viewpoints, despite containing important and relevant points. After peer feedback, there was a marked improvement, with students presenting their arguments with greater clarity, breadth of information, and creativity. This suggests that peer feedback helped students refine their argumentation skills, making their points clearer and more comprehensive.