Rhys Healey has joined Dundee on a loan deal until January, while Simon Ferry has left the club by mutual consent.
Dundee have signed Aston Villa youngster Riccardo Calder on a four-month loan deal.
Aberdeen equalled their best start to a league campaign as they won 2-0 at Partick on Saturday, while Hearts lost 3-2 at Hamilton.
Premiership Dundee, Hamilton and Partick were all dumped out of the Scottish League Cup at the second round stage.
The SPFL mascot race ends in controversy with the winner being a guest entry who didn't belong to a football club!
Hearts maintained their perfect start to the season with a comfortable 3-0 win over Partick Thistle at Tynecastle.
Hearts maintained top spot in the Scottish Premiership with a 2-1 victory at Ross County on Saturday, while Aberdeen won too.
Dundee scored twice in the final 13 minutes to earn a 2-2 draw with Dundee United in a thrilling match at Tannadice.
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