Delay during reproduction program

[CiscoTek]

Hi everybody, i have a problem with my blocks, wearing in some costumes for show dance. During the reproduction, 2 slaves start to have delay in the program, so the show it is not synchonized. Some ideas why? The work space is usually a stage, 10x20. Also what's the best variant for the antenna and the shape? i can't keep is streight, blocks are wearable and there's no way i keep it streight. modules are iqled v1.1 and the second should be led master mini (it's green, small and round). Thanks for suggestions