Slow Leak... Where to start...?

[Grove]

Hello,
My hot tub which I recently acquired and got cleaned and set up after acquiring it in a home purchase seems to be leaking.
Upon checking the chemical levels I noticed that the filter was making a sucking air noise which is when I noticed the water level had dropped. I noticed this once before, thought perhaps it was just displacement due to us getting in and out, and topped it up. This time I am confident it's a leak as it was down a few inches from where it was at after our last use a couple nights ago.

I inspected the visible pipes around the pump and the knife valves and I see no signs of leaks there and am not sure where to look next.

I've attached two pictures of a plastic piece which came loose. I do not know the actual name for whatever this part is, please accept my newbie ignorance. I am not sure if this part coming loose would cause a leak as it has no rubber gasket and I am not sure it is supposed to be water tight or not. It is 1 of 4 and it came off after I refilled the tub and I figured I'd get it back on eventually. Could this be a source of my leak?

Where else should I be looking?

Appreciate any advice.

 

[Swampwoman]

Hot tub leaks can be tough to find. I have a very old hot tub that ive managed to keep going long past its best-by date via finding and fixing leaks

If you remove your panels and look for damp areas you can get a clue.
One notorious leak location on older spas is the spa light...check the back of the casing on that. If its leaking, you will need to replace the light unit.

For inaccessible leaks in the lines behind hard insulation, Ive successfully used a product called Marlig's Stop Leak. It comes highly recommended and worked great for me.

But in the past, I've remedied other slow leaks by following accessible lines to the pump and snugged those fittings up.

Best wishes on your quest.