Yiimp public APIs don't seem provide current network/block difficulty, you'll want to use Soothaa's Coin Plugin and stay away from built-in Yiimp pools, reason being (not sure if it's fixed but right now it's Working as Intended) that the profitability data returned from the predefined Yiimp API overrides individual coin's profitability. Also Yiimp pools like zpool will redivert you to its own determined most profitable coins and convert to your coin specified in (-p c=XXX) with that, comes conversion fee. and you are not really mining that coin...you mine any coins of that algo and they gets converted based on market rate then you cash out and convert again when you want to sell them....that's why I say stay away from auto-exchanging Yiimp if you plan to convert yourself at later time yourself sees fit.

let me put this in picture:

You are mining say, Neoscrypt coins that are currently not the most profitable, so AM switched you away to other algos. but next minute, you are mining GoByte on 1 miner, and Innova on another, and you are wondering why it's all over the place. The situation turns out clear that suddenly Zpool reports highest profitability on its Neoscrypt pools, and it overrides all Neoscrypt coins which you have custom pool setup with the same profitability info.

You suddenly see something like:

Zpool Neoscrypt @ $5/day
GBX @ $5/day
CRC @ $5/day
DSR @ $5/day
INN @ $5/day

even if you have coins info correct and individual pools setup....on different pool, the result is, some of your miners mines at Zpool, but some mines individual coins at the obvious wrong profitability at another pool.