not really sure, it could be nutrient deficiency, or maybe a virus. i dont think it is ring-spot.

Even with viruses, they are often caused by the plants defenses not being strong. kinda like us having a weak immune system.

Papaya like lightly moist soil. not too wet. they need to dry out a bit between waterings. They also need organic matter. In the spring especially, they grow FAST, which means they are taking up nutrients fast.

is it in a container ?

Whats the soil like ?

They love compost, worm castings, used coffee grounds (older is better), fish emulsion

ive seen great results with diatomaceous earth too. it is more fine than most rock dust, so the microbes convert it faster. its also high in silica, which herbaceous plants like papaya need a lot of. Because papaya grows so fast, this makes a big difference.

They also seem to like a heavy mulch layer around the trunk , the wider the better.

Yes, it's in a self watering container with with potting soil and I added coffee grounds on occasions. The soil looks alive with worms. I have another plant in a 5g pot that is also showing the same symptoms.

on the bottom side of the leaves I can see brown critters or maybe fugus that seem to be eating the leaves from the center and the leave never get a chance mature before falling off. Now my small fruit has fallen off too. Here a close up of the problem.