Stains on ceiling

Thanks for the replies, the stains are from one side to the other in the shape of the ceiling joists. Every joist , and only at the joist.i don't think if they were from water that the stains would be so straight and even.every joist has the same even stain.its like the glue used to adhere the panels in place actually bled thru.I did try a magic eraser with no results . The ceiling is also very dry , I am able to access the joists above the ceiling panels thru multiple locations and the attic area has no sign of any moisture

This is a perennial topic because RVs have a lot of minor leaks. We use Oxyclean, a Clorox product. It has worked on all our stains. Take care not to get it in your eyes or on wood. When cleaning a stain from a leak, be sure the leak is fixed first or you'll be doing it again!

I had noticed something similar in mine. How large in circumference are the stains? Quarter, dime or larger? Upon close inspection mine was were they used some type of filler to hide the holes create by the staples used to secure panel to ceiling joists. The filler discolored after a few months and turned a tannish color.

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To help get rid of the stain put a small amount of bleach in a spray bottle and the rest fill with water and just lightly spray it. Do it lite and several coats. Let dry and usually will make it white again.

My thoughts are you have a leak or two. Brown stains are caused (usually) by water and the glue and wood mixing.

If its a 2013 and has never had the roof resealed, that is likely the problem.