I have create 4 droplets with 1 core 1GB ram on Debian 7.0 64 bit then I start mining in fast-pool.com by create 4 workers. but when I run it. 4 workers cannot be active at the same time. one or two workers can be active at the same time. When worker1 is active, the lefts isn't. When worker2 and worker4 are active, worker1 and worker4 aren't. I am curious how to activate all worker at the same time.

Thank you for you help.