Let's work on the leaf-critters.
We can probably use the stirge as a basis for the singular leaves, although the leaves are probably Diminutive.
Here's a rough draft...
Diminutive Plant
Hit Dice: 1/4d8 (1 hp)
Initiative: +4
Speed: Fly x ft. (x)
Armor Class: 18 (+4 size, +4 Dex), touch 18, flat-footed 14
Base Attack/Grapple: +8/+3 (+15 when attached)
Attack: Feeding-tube +16 melee (1 plus attach)
Full Attack: Feeding-tube +16 melee (1 plus attach)
Space/Reach: 1 ft./0 ft.
Special Attacks: Attach, blood drain
Special Qualities: Low-light vision
Saves: Fort +8, Ref +8, Will +4
Abilities: Str 1, Dex 19, Con 10, Int -, Wis 11, Cha 1
Skills: -
Feats: Weapon Finesse
Attach (Ex): If a singing tree leaf hits with a feeding tube attack, it latches onto the opponent’s body. An attached leaf is effectively grappling its prey. The leaf loses its Dexterity bonus to AC and has an AC of 14, but holds on with great tenacity. Leaves have a +12 racial bonus on grapple checks (already figured into the Base Attack/Grapple entry above).
An attached stirge can be struck with a weapon or grappled itself. To remove an attached stirge through grappling, the opponent must achieve a pin against the stirge.
Blood Drain (Ex): A singing tree's leaves drains blood, dealing 1 point of Constitution damage in any round when it begins its turn attached to a victim. Once it has dealt 1 point of Constitution damage, it detaches and returns to the singing tree.