Forum:Koa'ki Meiru Skill Drain...?

At a local tourny... i heard that even with Skill Drain Present on the field... Koa'ki Meiru Wall, Koa'ki Meiru Sandman, and Koa'ki Meiru Gaurdian, can still use there effects to tribute to negate. Is this true?

Also, is the requirement to keep them around by revealing a rock monster in your hand or by discarding an iron core negated by skill drain, or is that a cost that is unavoidable?