Add the letters a,b,c etc to distinguish between the different sources in both the citation and the corresponding reference in the reference list:
Petty (2021a) sets the scene for neonatal nursing in reviewing the events that shaped 2020. An arts-based storytelling approach is taken to explore parents' stories of their experiences in having their baby in the NICU (Petty, 2021b).
Petty, J. (2021a) Council of International Neonatal Nurses (COINN): News Page. Journal of Neonatal Nursing, 27(1), 63-65.
Petty, J (2021b) Using arts-based digital storytelling in neonatal care to enhance nursing students’ empathy. Nursing Children and Young People, [Advance online publication]. Available at: https://doi.org/10.7748/ncyp.2021.e1351 [Accessed: 15 March, 2021].