I'll give it a go on 2 of these

-1- (whales/dolphins/minnows): Each voter has a different level of power depending his Steem Power holdings. Very large stakeholders of Steem Power are called "Whales" due to their big impact when they vote. Minnows are typically new users whose voting power is very small. Dolphins are somewhere in the middle.

-2- A post may be losing value (or increasing in value) due to fluctuations in the price of steem and/or the voting occurring in other posts - as all posts share a common reward pool.