Hi welcome to the forums
You show a good level of skill on these ships, that said i have a few nitpicks:
1st ship:
The colouring on the middle two sections is more pastel rather than lighter I know your trying to create depth but it hasn't worked there, good section usage but I'm not sure about combining all of the Kae sprite packs, you have almost made it work here but not quite some parts look messy. Other than the core showing (which is just a personal dislike) and the orange blaster at the front its quite a nice ship.
2nd ship:
I love the side pods on this ship really good use of mecha sprites, and then its got this dark stock sw section in the middle which ruins the flow, i also feel the big blocks of green break up the flow. the large circular piece at the rear could be replaced with a different sprite, other than that i really like it.
3rd ship:
Clutter, clutter, more clutter and then i saw a ship! Its not bad could be better don't really like the back at all or the gap at the front, it feels like it could be stretched out to create a pointier ship (which from the current evidence is your forte) and you should download some groovy exhaust sprites or something to make it look a bit prettier (although I'm sure you have thruster ex modules on it if your metagame balancing.)
4th ship:
Apart from the middle area behind the bridge, the two green generic sections (which I would love to see replaced), and the over saturation of the blue from the hangars, this is a good ship, it has a very smooth shape but I'm not sure about the edges of the wings I feel they could be smoother. all in all nice
5th ship:
The engine pods are nice the rest of it makes me hurl, lets be honest its a hammerhead shark with a massive hexagon in the middle and an ass that looks like it got bitten by a rabid squirrel. I just don't like this but its your ship so no worries.
If you don't like anything I've said no worries, I don't either. And your entitled to your own opinion etc etc etc.