The estranged reality star couple have reduced the listing for their estate once again ... coming down from $5.5 million to $4.5 million -- about a month after they brought it down $500k from $6 million.

You know the drill by now ... the pair's got money issues -- with multiple financial lawsuits pending, and the IRS is coming after KZ and KB hard. Selling the house could be a saving grace for the couple ... however, they seem to be having trouble unloading it.

Keep in mind ... houses in the area were going for way less money than what they listed it for when they made the first price cut in December, and they can only hope this new price drop will entice a buyer to take it off their hands.

These financial struggles are causing a massive strain on their personal relationship too ... we broke the story, body cam footage from November showed a nasty fight between the couple in which Kroy blamed Kim for their financial struggles while also accusing her of "f***ing other men."

They've since calmed down enough to continue living in their shared space (unclear if they're still hooking up like they were right after Kroy filed for divorce for the second time) ... and KZ even made sure their kids got Christmas gifts despite their financial woes.

Kim & Kroy bought their mansion back in 2012 for the bargain price of $880k, so even $4.5 mil would be an impressive ROI for them ... but they really gotta sell quick because Truist Bank says they defaulted on their mortgage -- adding the bank is well within its rights to foreclose at any time.