'All My Children' Actress Marcy Walker Battling Mysterious Health Issue

Soap star Marcy Walker -- best known as Liza Colby on "All My Children" is in need of "serious medical care" ... this according to her former costar.

Word of Marcy's health issues first got out back in May, when her "Santa Barbara" costar, A Martinez, addressed why they were charging for their June 7 live stream.

Martinez said in an Instagram video ... "Marcy has been ill and is working hard to get well."

He explained Marcy "has come face-to-face with the financial challenges that so often plague those of us unlucky enough to need serious medical care in our country."

The actor didn't elaborate on Marcy's condition ... just explained why she needs the financial support.

And last week, a seemingly fan-made GoFundMe popped up to raise funds for Marcy's medical expenses.

The crowdfunding page says she's dealing with "an ongoing health issue" and she "urgently" needs help with money.

The organizers write ... "We want to surround Marcy with the same light and security she gave to us for so many years."

They say the money raised from the GoFundMe will go directly to Marcy and help with things like living, medical, and personal expenses.

Marcy left "All My Children" in the 2000s to work at a Christian Youth Ministry ... but she clearly left a mark on her fandom.