3880 black ink missing
Did you call Epson Professional support, or the number for SOHO printers? There is a huge difference. The SOHO support goes to some overseas call center and they are not very helpful!
If I were you, I would start by telling Epson that you have the exact same problem with two printers, and you wonder WHY that happened. Maybe you got bad ink? Perhaps you are storing your ink incorrectly? That might get their attention more than handling it as two separate cases of otherwise normal failure.
If you email Epson support through their web site, and indicate that you are having a bad support experience, have 2 broken printers, and need help, someone from Epson corporate will call you within a day or two. These people are not technical trouble-shooters, their job is to catch customers who might be falling through the cracks, and make sure that the support / customer service people are not losing your business!
Also when you talk to these people, mention that you have these two broken printers and have bought a third (if I read your post correctly.) They have a "customer loyalty program" where they give you free ink for being a repeat customer. I know what you really need is your printers fixed, and hopefully they can assist you with that also. But the customer loyalty thing is probably something most people do not know about -- I sure didn't until this week!
Good luck getting your printers working.