Just to make sure, you defeated the mech bosses in this world we're talking about, right? And it's in hardmode and all. Right?
If that's so, when did you defeated the mech bosses? Was it just now, or more in-game days ago?
You only need 1 mech boss down for life fruits to start growing. But it can take a few in-game days until you have a noticeable amount in the jungle.
It can also help, if you destroy jungle bushes here and there, to encourage the vegetation to renew, and maybe it will be something else to grows in the place where earlier it was just a bush.
It also can be a big help to have a metal detector, and spelunker potions. Metal detector will show the highest tier stuff. The jungle by that point is full of clorophyte everywhere, so it will almost always shows that, but sometimes it will show life fruits (and life crystals) when they're nearby. they might grow in previously undiscovered places, or areas where they're hard to spot, so spelunker potions can be a huge help finding them.
if you have all 3 mech bosses down anyway, might as well craft a drax or pickaxe axe, and mine some clorophyte too, meanwhile.
if you leave 1 clorophyte block there, it will grow into a larger vein again, over time. (you can also "plant" them yourself too, in mud, and they'll grow. only works below a certain depth though)
I will now go farm nymphs.