I looked and all three devices have MIDI in. You can buy a MIDI splitter and drive all three from one MIDI source, just set each synth to a separate MIDI channel (1-16).
At this point, you may want to consider using a DAW. If you get a USB audio interface with four inputs and a MIDI jack and inexpensive software like Reaper, you can manage your sequences in your computer as well as record/mix/add effects as well.
Just an option.