Asus' ROG Earbuds have been reviewed by Tom's Hardware, and the review points to the the Buds themselves for the lag you may be experiencing.
Of course if the phone's storage is at 99% that's only going to compound the issue.
"The Asus ROG Cetra True Wireless earbuds carry their own weight when it comes to audio quality and features. The one place they really seem to be lacking is the one place they shouldn’t be as a ROG product — THEIR LATENCY is just TOO UNRELIABLE for serious gaming."
