Can I ask, why did you add a ナ at the end of Collen and Madelyn? They would just end in ン, would they not? I think generally English names that end in consonants you’re going to end in the う sound. Ending them in an あ sound like you’ve done here doesn’t sound right.
Some advice I got a while ago, which I’ll repeat to you, is to check Wikipedia pages for famous people with those names. By going to the Japanese versions of those pages, you can find some katakana versions of the names.