I recently had a batch of dwarf hair grass die and of course upon testing tonight, my nitrites were at 5 and my ammonia was at .25! Up from 0 and 0. One of guppies died (unsure if it was nitrites or because they were new). Anyway, did a 25% wc and skimmed out as much of the dead grass as possible. How long should I wait to retest? Is there a recommendation on wait time?