I was able to get this working by introducing the following code in my view:
<% for i in 1..@customer.addresses.size %>
<%= f.fields_for @customer.addresses[i-1] do |a| %>
<%= render "address_fields", f: a %>
<%= render 'layouts/audit', audit: @customer.addresses[i-1] %>
<% end %>
<% end %>