Taking your birds to an avian vet would be your best option, since the problem could be anything from infection to toxicity to aging. How does their poop look? Is it normal consistance or does it look different? "Birds For Dummies" is a great book and has a very helpful section on avian illnesses. For home care, the book recommends that you use a smaller cage to make him less active, lower or remove perches and fold towels in the bottom of the cage, keep food and water close by, try to keep the bird warm - target range 75-85 degrees, strive for peace and quiet, and keep handling to a minimum so he can rest. I hope this helps some.
My senegal, Oliver, was only 4 years old when he developed symptoms like you mention. First I noticed he was sitting low on his perch, then I realized he was having trouble climbing. He actually fell off his perch on the second day that he looked sick. I didn't take him to the vet and he died a day later. I put a towel at the bottom of his cage (since he could no longer perch) with a heating blanket on low under it. I covered the cage and kept the lights turned down to decrease his stress. I didn't follow the advice about handling though. I spent a lot of time holding my Oliver, and crying over him. When I was pretty sure that he was going to die, I carried him outside to sit on the porch and feel the sunshine on his feathers. I have my regrets about not taking him to the vet, but honestly, I don't really think they could've done much for him. It happened so fast.
Hugs to your birdies. I hope they come around. Keep us posted.
Amy