Well i don't know their 'name' but i managed to solo all the bosses except Queen since i don't 'get' her.
For the chicken--- Make him walk towards the Clocks he puts down. When they have black Dials, they increase your time. When they have White Dials, your time decreases (which is bad.) Make sure to have a ton of Ginger pots to keep your HP nice and high. His 'energy balls' seem to do 80% damage, and he does have a 1hko move when he jumps up after blinking and smacks the floor down. Keep your HP as full as possible.
For the Clown thing--- This guy is easy. Just make sure that if the crown you have on your head matches his, to not attack him(otherwise he heals). When he is spamming the fire move and you are NOT targetted, make your party members attack him as long as their 'crowns' aren't his color, rush him. It seems like you do about 3x as much damage when you do it at this time. Also when he blinks and disappears for a second, keep jumping away from him or he uses this Hammer type of move to 1HKO.
Vellum (snake thing)-- He's easy. Just watch the floor and try to get him down to around 80% HP. After that, he starts throwing fireballs. That's when you strike him down. Try to time it so you don't get knocked back onto a fireball, since that's a 1HKO move. My buccaneer had a little trouble here since it doesn't have a 'Jumping' Skill. He usually pop in and out about twice, then on the 3rd 'up' he starts spamming fireball. Really easy boss to beat.
The Queen. No idea how to beat her. I've gotten to around 35% hp on this one; but i just don't understand it.