Dear CH,
When the contest is in judging if you want to ask for changes for any designer you need to put that designer ranked first.... just the first ranked designer can send new versions of the logo.... you can switch anytime between designers and ask for the changes... you can ask for the changes with a PM (click over our name to go to our profile) or in our designer page inside your contest (clicking over our name to see all our designs).
Thanks,
Soumya