power tube replacement Mark 5:35 combo

[jaytime]

I recently identified a bad power tube and ordered a set of 4 EL84s. I noticed that all 4 EL84s that are in currently in my amp are "match group GRN" "code 10". The new tubes that arrived are "match group GRY" code "3126". I am wondering if I just can just change out the one "bad" power tube or if it is best practice to change them all out at once. Additionally, do I need to re-order so that I get the "match group GRN" "code 10" power tubes? Thanks in advance for any advice regarding this process.