What does it smell like? And, from what you can observe is the substrate is limited to the fruit? Infections in JAOM are uncommon, but not unknown.
Yeast cells often replicate on the fruit rind and drop from there. If it doesn't smell like nail polish or rotten eggs then you should be okay. If you're worried about it, give it a gentle shake to release the yeast from the fruit.
I had a JAOM not too long ago that was doing the same thing, and it turned out to be just yeast reproducing on the fruit.
Though, something worth mentioning. You do need to push the fruit cap down daily so that it doesn't dry out. If the fruit is dry for long enough, it's possible for it to become infected. But again, unlikely if you did everything right.