Where they under the floor joists or the main beam supporting the floor joists? What are the posts made of ? is the basement floor concrete or dirt. is there footers under the posts? if its on a concrete floor. is it cemented in? if its on the concrete is it sinking in? On average a main beam should be supported every 10 feet. But i have no idea what kind of system you have so i wouldn't rely on that. If you can my questions and take some picture we can try and help