I can't see the issue with the middle ones eyes tbh

I'm afraid I can't be very helpful. I'll just say that they almost look good at 1x, but the more I zoom in, the less sense I can make of the pixel choices. At 1x the only issue is the bright pixels look cut off in 2 clusters per eye, which zooming confirms, and the surrounding dark clusters get pretty smooth / over-AAed with no apparent structural reason (that I can think of). I'd have expected the bright clusters to be AAed more (by 'clusters' I don't mean strict monochrome clusters, just broad regions of related pixels).
Part of the problem may result from keeping some dark outline, esp. in the inside of her right eye.

I wish I could be more specific and offer solutions, but unfortunately the very few times I tried to pixel eyes I failed miserably.
The only general advice I'd give is to get rid of as much outlines as you can at these small scales, contrary to your usual work. The littler one is an example of this: the arms are all banded outline.

What Alcopop said.

Also you have lots of unneeded colors in there, many of which being used in one or a few pixels only (hover over the color patches to locate them).
Always try to reuse an existing color, and only create a new one when you have a compelling reason to do so.

Recommended reading

Good start, I like the dynamism here =)

The main problem is the size, which makes it unmanageable and also will deprive the final work from most of the pixel-art feel. I'd recommend something closer to 200x300.

The perspective might benefit from a 'fish-eye'-like view, with a curved bg, it would help read the 'folded' ground plane.
I don't know why the palm trees are aligned, if no reason there should be some in the bg (which will pose its own perspective challenge).
The lower right bug shouldn't be cut, it's not well seen at first; the triangle made by the two bugs + hunter is the main composition element and should be carefully thought out.

Shading is weird, there's an almost pillowshading-like technique of concentric, equidistant tone bands regardless of light source and shape.
See for instance a typical cylinder shading, compared to your palm trees:

The highlight area is wider than the next shaded areas.

The light source on the lower right bug is from below left, from front left on the hunter's belly, and from above left elsewhere.
The way the trees shading progresses from left to right would imply a very close source, like a candle.

The palette looks like it suffers the classic mistake of independent color ramps, with little or no hue- and saturation-shift.
It's hard to study though because of the NPA title area which messes with color count tools. Can you post a pixel-only version?
More about palette building here and there.

Any cheap tablet is good enough for pixels, I think. But if you do other kinds of digital art, a good tablet is worth it. Small tablets (A6) are good for any kind of work except large life-like drawing gestures.

Draw from life, otherwise you'll always depend on somebody else doing the hardest part of the work (composition, perspective, light). Even more than that, you need to unlearn how you think things look like, and just look at them as if you had never seen them before and had no idea what they are. Only this will teach you how they do look like.

Using refs is great but should be restricted to getting info about how to draw things that are not readily available, not whole images to copy.

I think the point of both color edits is to show you that your colors are too 'basic', in a mental kind of way, and thus neither realistic nor visually striking: you need to get rid of the 'grass is green, earth is brown, stone is grey' mind set.
Look at reference images, or actual nature and look at the true colors that are actually there, especially those which are 'at the edge' of perception, like blue/purple shadows.

You have 19 colors, the last one (grey) likely accidental as it covers one pixel only (I couldn't find where). A piece with that much detail can have 32 or more without shame (if needed, of course).

Your color ramps (greens, browns etc) have very little hue shifting, they are disconnected in both color space and pixel space. Also you should avoid the use of pure (or nearly pure) greys: stone is rarely neutral. There are no dark tones.

Think of your palette as an interconnected whole, and recycle colors throughout the piece. More about this here and there.

The composition is good, but it makes the tree more the focal point than the building, which kind of contradicts the color balance (and maybe your intentions): the viewers eye is a bit torn between both.