Framing and Sub-Flooring - bathroom sub-floor

My house is probably from the 1920's in northern NJ; I am currently re-doing my kitchen ceiling due to the fact that sections of the ceiling blistered. This I believe is due to the fact that the bathroom is above the kitchen as 1 of the blistering areas is below where the toilet sits and the other area appears to be where the radiator pipe comes thru the bathroom floor(steam heat). When I opened the ceiling there is a section under the bathroom that is framed out in 2x4's attached to the 2x8's with t&g planking boards above the 2x4's. Sitting on the planking appears to be a cinder slab and the planking is hindering my ability to see the underside of the toilet plumbing(lead band and cast iron piping). Basically my question deals with this cinder slab and 2x4 support network; will removing it make the bathroom floor (tile) unstable and cause it to collapse?
Thank you in advance for any information forwarded.
George Schreck

If there is a mud job on top of the tongue & groove planks, you certainly don't want to remove those supports. Does all of it look original? One way to tell is if the 2x4s are really 2x4. Do you see what's leaking? Get a good light & look closely for signs of water.