楼主仅仅催稿还不够，还要搞清楚稿件目前的状况，搞清楚到底速度慢是慢在哪里了？然后有针对性而不是泛泛地催稿。

用通讯作者的邮箱登录投稿系统就应该可以看见。

既然你催稿催过两次了，建议不雅再催稿了

你现在的稿件有进展吗？这个从提交到第一次收到评审意见得多久？

耐心等吧，实在担心的话可以询问：
Dear Prof. XX,

I am sorry to trouble. I submitted our latest work (No.XX-00029) to your journal on March 4. But it current state is still "under review" . I want to know the review process. If there are some responses from the reviewers. Would you please tell me the results so that I can deal with it as early as possible?   

I appreciate your contribution to the publication of the high quality papers.

Kind thanks to you for your care.

Best Regards，