Quite a few acid soil loving plants develop this problem in soil with a pH that is too high for them. A little bit of fertilizer designed for azaleas and rhododendrons might help, as they contain the iron the plant needs, in a form it can get to. They cannot get to the iron in regular soil if the pH of the soil is high.
Many evergreens have leaves that last two years and then the older leaves turn yellow and fall, but in checking my laurels, this is not the time for that.

I did fertilize all with a fertilizer for acid loving plants. Worked on making sure it was spread around evenly, too.

is it deciduous???

best guess:.. something was wrong with this plant in the pot.. perhaps circling or girdled roots.. and it is struggling to get ESTABLISHED.. as fast as the others ...

and due to such.. it suffered a worse summer than the others.. it simply could not cope..

short of digging it up.. and finding out whats wrong with the roots.. i doubt any any amount of fert or soil amendments is going to make a difference ... and frankly dumping either on mere speculation.. borders on pollution after a while.. you have to react to a crisis.. not really guess at a solution ...

i would wait until late spring to see if it buds out with vigor.. and if not.. i would dig it up and find out why ...

but you would probably be better off doing that now .. why wait ... and if its under warranty.. talk to the seller now ...

ken