Gladys Knight‘s fans are deeply concerned she’s being forced to perform shows after she looked totally out of it at multiple concerts, and now people working on her tour are calling it absolutely “tragic” … TMZ has learned.

The Motown legend has been touring solo, and sometimes with fellow icon Smokey Robinson, for several months, but after the last few shows Gladys has looked confused at times, staring off blankly and leaving much of the vocals to her backup singers. Her July 25 show at the Hollywood Bowl featured one of the more concerning incidents.

Sources with direct knowledge of the tour tell TMZ … people spoke to Gladys’ team before that show and said it’s “not suitable” for her to be on stage.

Once the show started, it’s obvious why they were worried … while performing her classic “Midnight Train to Georgia,” Gladys turned her back to the crowd and started walking off the stage. When a backup singer reached for her arm, Gladys shook off the attempt to keep her on stage.

One source told us her Las Vegas tour stop with Smokey, back in April, was even worse — and some people working the tour feel like she’s showing symptoms of dementia. The source said it’s “shameful” the 82-year-old is being trotted out on stage night after night.

Gladys is managed by her husband, William McDowell, who tells us Gladys wants to keep performing, but he says she has good days and bad. As he put it, “No one is ever gonna make me say, ‘My wife is well,’ but all she wants to do is sing.” He says she has not been diagnosed with dementia, but they’re going to a doctor in the near future to evaluate if she has that condition.

The reality is Gladys’ voice is still strong, and she does sound great when she’s able to sing. She has tour dates booked through mid-November, but McDowell says he’s eyeing her Sept. 5 show as a key one — telling us if she has a rough night, he’ll pull the plug on her remaining dates.

Some concertgoers who saw her perform in Detroit think it’s past time to end the tour. After she took multiple breaks off-stage, and appeared exhausted, several fans left the show early because they didn’t want to see her in that condition.

McDowell seems to acknowledge tour life is too much for Gladys, though, because he says he’s building a facility close to their North Carolina home, so she can continue doing shows without being on the road.

Right before we posted this story, McDowell sent us a statement from Gladys, saying … “After much soul searching I’ve decided that I will be easing into fewer performances while focusing on transitioning into the next stage of my career and life moving forward. I’ll be spending more time on projects with my husband and visiting with my grandbabies and am looking forward to this new era.”