Serious Question

My elderly neighbor has a large lemon and tangerine tree growing in her yard. The trees are next to each other. A couple of years ago the lemon tree produced real large lemons and the tangerine tree produced real sweet seedless tangerines. Last year the trees grew some awful fruit that were neither lemons or tangerines. The fruit did not look like a lemon or tangerine and they were loaded with seeds. My other neighbor told her to get son to saw off the suckers that the trees were producing. She forgot to tell her son and this year both trees produced fruit that looked like huge lemons. She gave me one so I could tell her if the fruit was edible. I brought the fruit inside and cut it in half. The fruit contained a few seeds but I'm not brave enough to eat it. I licked the cut citrus and tasted the juice. The fruit did not have a smell of citrus and the juice was a mixture of sweet and sour. I told her if they were my trees I would simply remove the fruit and trash the fruit. The fruit isn't worth keeping. I also told her that I would saw off the suckers for her at the right time. Oh, the suckers have large thorns on them and they hurt like hell if you get stuck by one. What do we need to do to get the trees to produce great tasting fruit again? I'll do the work since this lady is very old. I just wish that her trees would start producing again before she passes away. I don't know much about growing trees or outside plants and I'll admit it. I'm just a pro at growing orchids that supposedly aren't able to grow down here. I devote all of my time to raise the orchids in my collection. I really want to help my neighbor so if anyone knows what happened to her trees, please share that information with me. Thanks