Decision in process has passed a one month. Should I send a mail asking status of manuscript to editorial staff?
The straight forward answer is NO. This is because of the following reasons:


the journal you are talking about is highly reputed and the editorial office know their responsibility well.
30 days is very less given few situations where two or more Editors taking final decision. So it includes communication times.
although you have adrenaline rush to see the review results. It is better to wait to show that you are not desperate. (I understand it is difficult)
instead of mailing them better start working on what possible comments the work might have got. So that you can finish the revision soon, if Incase


Last, good luck!