Why didn't the Quran say "Your Lord" (plural, addressing a group) and "upon you" (plural, addressing a group) instead of "Your Lord" (dual, addressing two) and "upon you" (dual, addressing two) in the mentioned verses?

These verses address humans and jinn. They are preceded by Allah's saying: "O company of jinn and mankind, if you are able to pass beyond the regions of the heavens and the earth, then pass. You will not pass except with authority [from Allah]." Al-Tirmidhi and Al-Bazzar narrated from Jabir that the Messenger of Allah, peace and blessings be upon him, recited Surat Ar-Rahman to his companions and said that the jinn had a better response than them, as they said: "Of no bounty of Yours, our Lord, do we deny. To You be all praise."