The copper cattle were under the Yam (Melachim I, 7:25). They were not under the Mechonos!
Rashi: The verse means that they were near the Mechonos.
Radak: The verse is abbreviated, because all this is in Sefer Melachim. The cattle were under the Yam mentioned above in this verse, and the Mechonos were under something (the lavers), but it does not mention under what. Many verses are like this, when one can understand [the intent].
Why does it say "Asher Asah ha'Melech Shlomo"?
Radak: There were not others. The Kelim that Shlomo made in the Beis ha'Mikdash were there until the Churban.
Why does it say "li'Nchushtam Kol ha'Kelim ha'Eleh"?
Radak: The pronoun (the suffix Mem) precedes the noun (Kol ha'Kelim ha'Eleh). We find like this - "va'Tir'ehu Es ha'Yeled" (Shemos 2:6).