Wiring multiple peltier units
Supply and load are both 12V so that means you will need to connect everything in parallel.

BUT since the TEC uses 15A you can only connect ONE to the supply as the supply can only deliver 25 A. When Connecting 2 TECs in parallel you need a supply of: 2 x 15 A = 30 A. Your supply is 25 A which is not enough.

So you can only use ONE TEC with ONE supply. For the second TEC you will need another supply OR ONE more powerfull supply of 12V and at least 30 A and then connect everything in parallel.