This might sound weird... but...
For the last couple months I have noticed that all three of my beardies (who are housed in three separate tanks) all go to the bathroom within two minutes of each other. I find that really funny and well, odd, as I cant explain it. Maybe its the smell in the air? Or their feeding schedule? But, literally, within two minutes all three have pooped.
I am actually getting mine to do this too! Well really when I give them their baths... But If I don't get them there fast enough they both seem to go at the same time too.. And they are also in separate vivs. They will go within seconds of eachother when in the tub though.. I soooo like that much better!!