Once again, the lead needs to be expanded to summarise the article. A couple of sentences on its career and a mention on when it was commissioned would be good (you can ignore the latter if you think it's best)
"The ship also mounted two twin, above-water, mounts for 21 in (533 mm) torpedos" - torpedoes
"The walls of their conning tower were 6 inches thick" - convert to millimetres
converted on first use.
"... on 21 July 1913, launched on 23 February 1914, and completed in January 1915." - I think this sentence could be broken in two. ...on 21 July 1913. She was launched on 23 February 1914, and completed in January 1915. Feel free to ignore this, but I thought that the previous sentence was too long to read comfortably
Agreed.
"In early August, Cordelia and her squadron" - of what year? 1915?
Yes, as mentioned a couple of sentences earlier.
"Later that month, Cordelia was reduced to reserve at Devonport. By 1 May" - this is the beginning of a new section, so I lost track of what year this was. It might be best to start this with Later in February 1919, Cordelia was reduced to reserve at Devonport. By 1 May
It's in the immediately preceding sentence, so I don't think you're giving enough credit to the reader.
"she recommissioned for service in the 2nd Light Cruiser Squadron in the Atlantic Fleet" - link Atlantic Fleet (United Kingdom)
Linked in the lede.
"and placed in The Nore Reserve" - 'the' needs no capitalisation