JELLYFISH OLOLOL

[Vaati]

You should study more pokemon designs. Starting with their eyes. The eyes of the first and second jellyfishes from the evolution line are p.cool, but the third one should give a feel of intimidation. This expresion feels kind of dull and strange.
If I were you I'd draw eyes of a similar style to those of Haunter and Voltorb, but without the pupils.

Also, I'm not a big fan of this colour scheme either. Remember that also, when Pokémon evolve, their colour scheme often changes some. I'd personally use a slightly desaturate blue, purple and yellow/orange for the first one. The second one would have a dark/strong blue, purple and orange/green, and the third one would have the same dark/strong blue, purple, orange, green and black.

Do remember too that when they evolve, pokemon tends to get less cute/geometrical and more detailed and beastly. Study how jellyfishes look like, after all, all pokémon were drawn over animals' basic anatomies.

So yeah, pretty much that, study the style behind pokemon, look at lots of jellyfish pics and try to make your pokemon look a lot like them, even in little details - which you should definately add. More details, more colours, more creativeness by adding more concepts over the pokemon (like Venusaur which is a dinosaur with a plant growing on his back, Blastoise which is an armored tortoise with cannons equipped on his shell, etc).
And yeah, pretty much those. So far, the design is too simplistic and non-pokemonish.

I have to disagree with Ya on that one not all Pokemon get less cute when they Evolve take Bellossum, Sunflora, Roserade, Togetic, Wigglytuff, and Blissey for Examples they're still cute