You need all yellow mana shards for the one down the pit, make sure not to mix yellow and cyan. As for the purple one, the green mana pellets are only there so you can mix them with the wrong shape purple shards.
Drop rate is luck dependant, but you can get more drops by getting high combos. Fish spinning is how you can harvest scales from fishes in the ocean, you'll have to look for the green ones to get the rare scales. As for the cyan puzzle, did you solve it as yellow first? You won't be able to do the cyan solution otherwise.