I think that approach on the colouring of the lemon just feeds into the generally unpleasant and murkiness that is dark pure yellow
something like this is both more realistic and more appealing on the eye in my opinion
which brings me to another piece of critique, I think the fruit looks a bit flattened and warped in your sketches and consequently your pixels, some more than others, and even if the reference was some rather oblong fruit it should be avoided because it's not the widely associated traits of said fruit, I've shown one suggestion on reintroducing more a more round and volumetric form in the edit.
the closest thing I could think of to explaining what I'm seeing is this:
in this example, imagine you are trying to achieve a sphere and you let people know you are trying to convey a sphere, if it wasn't known by other's what you are trying to achieve it wouldn't look off, but once we have a point of reference and know what it is intended to be they realize it doesn't look quite right, knowing this is what you intended
also there is also a case of not terminating the edge of the object's silhouette properly and stretching details out, which make the viewing angle look quite off, and it's what alot of artists go through in my general observation, i struggled with it early on too, here's something to illustrate
hope it conveys what I'm observing, just making you aware of it, because it'll be all but impossible to address if you weren't aware of it.
other than that the colour and texture looks pretty solid continue
