The new growth is showing iron deficiency which can often be caused by high soil ph.

Very common on gardenias, look for an "acid" fertilizer that contains iron such as MirAcid by Miracle Gro though there are others.

Since we don't know where the OP lives, it is impossible to diagnose accurately. Nonetheless, it looks to me as well like chlorosis. Iron chelate for fast green-up, acidify the soil prior to planting any more.

Dan

Thank you for the quick follow ups. I'll get some acid fertilizer/iron chelate to address the yellowing. Are the brown spots a result of the chlorosis as well?

thanks,
dthroop

the brown spots are an external injury to the leaf... it has nothing to do with the other suggestion ....

how it.. or what happened.. is speculative ...

in my zone.. that would be cold damage ...

in yours.. water drops on a particluarly hot day when the leaf was very young.. and the sun heated it??

chemical lawn spray...

so many options.. i doubt you will ever really know ...

but the rest of the plant looks fine.. if it were me.. i would leave them ... if you want to pick off a few leaves i dont see where that would hurt a large plant ...

ken

Thanks, Ken. We did have a pest control treatment the other week, and that's the only chemical I can think of that might have caused any damage. But, as you noted, there are many possible options. I'll pull some leaves off of one plant and keep an eye on it.
Regards...

where do you live? is the gardenia in the ground or a pot?

That sort of necrosis could be several things, but if the spots appeared suddenly, you'll want to change consumer pest service companies.

Dan