Sometimes coins will be shown as zero value because they are offline at the exchange (wallet needs updated?  exchange on fork? etc), or a few other reasons.... Usually if they aren't planned on being a dropped coin, the pool will sit and nibble on a block or two here and there to get shares in the middle times of larger diff coins.... [crackfoo's nuts at the bar analogy comes in here], and when they finally get fixed/online/whatever, you get the big bump in credit when the funds are sold/sent to the exchange.   I remember this happening before.