Looking at your page, the reason you can't use css=div.Select-placeholder input
like you have with the first field, is that the input is not a child of the placeholder element. You'd need to use some xpath like this //div[@class='Select-placeholder']/..//input
which would find the Select-placeholder
element, navigate up to the parent element and then find the input. However the issue there is, that there are multiple input fields which match this.
You could use: (//div[@class='Select-placeholder'])[1]/..//input
replacing '1' for whichever instance of the element you are targeting, but if you can I would recommend amending the code of the page itself to make each input field uniquely identifiable (adding on id tags for example) as it would make your automation less brittle and likely to fail if the order of these inputs needed to change/more were added etc.