Without being an expert on Jacuzzi-specific plumbing techniques, I would almost guarantee that there IS a manifold connected to the air control. Sorry if this goes back to the basics...
Basically each jet has a water line and an air line which feed it. Becase the jet has a venturi inside, when you force water thru the jet from the pressurised water line, a vaccum is created that sucks air into the jet thru the air line.
Now lets just say that you take a flexible pipe from the air inlet on this jet, stick your thumb over the end, and turn the jet on. If you remove your thumb from the end of the pipe, the jet will suck air down the pipe, and allow the air bubbles to mix with the water, making the jet more powerful (just like using the air control).
Now to save having a separate air control for each jet, every jet in an individual seat will be fed by a pair (water and air) of manifolds for that seat. If there are five jets, then the water manifold (around 40-50mm dia) will then break down into five 1" fingers that pressureise the five pipes supplying the five jets with water.
There is also then a smaller manifold (around 1" dia) which splits into five fingers, with a (approx 1/4") pipe going from each of the fingers to the five jets. Now if you turn on the seat so the five jets are working, you can put your hand over the end of the air manifold (to stop air being sucked in) and the jets will just push water thru. If u remove your hand from the end of the manifold, then the five jets will all suddenly become more powerful and allow the air to be sucked into each jet.
I suspect that the manifold for the air is perhaps not right next to the Air control. I think that the air control probably attaches to a length of pipe, which will then connect (somewhere else) to the manifold.
So I think what you need to do is just replace each of the Air controls in turn and reconnect them to the pipe feeding the manifold.
I've attached a picture of a spa in production to show the two sized manifolds (water=large, air=small). Note: In this picture, you will see that the air manifold attaches directlty to the underside of the air control valve.
If you are working on your spa and want to avoid too much replumbing, a good trick is that by VERY CAREFULLY, and EVENLY heating the fittings/pipe up, you may be able to remove the elbow from the other pipe (or remove the pipe from the elbow) so that you can recycle the parts/pipe and avoid ripping half the plumbing out for each repair.
An example of how to do this:
To remove a piece of pipe from an elbow... Where the defective pipe leaves the elbow, cut the pipe off using a hacksaw (or reciprocating saw), so that there is no pipe sticking out of the elbow, just the last little piece that is still glued inside. Take a heat gun and evenly heat this pipe up until it starts to discolour and bubble. Now quickly (while the pipe is still soft) use a flat bladed screwdriver and force it between the pipe and the fitting, levering the pipe and fitting apart so that there is a screwdriver shaped gap. Stick some round nose pliers into the gap, so that they clamp both sides of the piece of pipe. Now just rotate the pliers, in a circular motion so that they peel the pipe off the inside of the fitting, and you end up with a clean(ish) fitting, and a load of melted pipe wrapped around the end of the pliers. Then you should be able to glue a new elbow onto the pipe using plenty of glue, and still get a perfect seal.
Hope this helps you get your hot tub sorted!