In March 2018, Twitter announced they'll be changing their API to "limit the ability of users to perform coordinated actions across multiple accounts.". Twitter's guidance explicitly states "...Do not (and do not allow your users to) simultaneously post identical or substantially similar content to multiple accounts. ...".

You will no longer be able to publish, schedule or queue the same tweet to multiple Twitter profiles simultaneously. You will also not be able to schedule a tweet to multiple dates at once. As Twitter's announcement states, 'an alternative to posting identical content is retweeting content from one account to another.'

You can still publish to Twitter and other social networks simultaneously.

This change applies to all 3rd party tools that use Twitter API.