Can I contact other sellers to ask them ...?

[mabelma]

Communication between sellers should be reserved for the forum, not only are you not invading anyone's time but the pool of possible experts is that much larger than having to ask literally one seller at a time. So yeah, keep it on the forum. 

[saimii]

Ita a good try to educate a few, but a specific group of Sellers won't bother to read it. Only affectees would be reading it. 
Sometimes, They will come just to ask about suitable plugins for the required feature and pretend to be a buyer. If you respond to them nicely(out of courtesy), you must answer them for all their issues. 

We don't click spam to avoid issues with their account, but they won't understand it until someone does the same with them. 
 

[canopygallery]

Fiverr does offer this caveat: "

Partner with other freelancers

Quote

"The truth is, if you’re having trouble knowing how to best promote your freelance business, other freelancers in your network may be struggling with the same issue. So partner with them. Find freelancers that offer similar services but to a different target audience. Then, when you have a client that’s not quite the right fit for you, recommend your freelancing friend instead. They’ll do the same."

 10 profitable ways to promote your freelance business

[asmatkh]

Don't as my friend's account has been flagged as spam for his messages to other sellers.