They're in that picture, 4 small silver cylinders about halfway up the right side of the image. "Orange Drops" tend to be on the larger side which is why they really stand out compared to the original caps.
Coupling caps prevent the DC voltage from a previous amplification stage from being passed to the input of the next stage. If they start to fail ("leak" voltage) the power dissipation of the downstream tube goes up, essentially wasting a bunch of power amplifying nothing. I'm guessing those are the output tube coupling caps which are extra important because if they go bad it can take out tubes and output transformers.
Everything else looks original. Replacing coupling caps is a good start but I would definitely budget for some additional recapping in the near future, if the coupling caps were getting leaky I suspect there are a bunch of other caps that aren't far behind!