[Refinish Western Red Cedar Hot Tub (Inside)]

I too damaged the interior of my cedar tub and have been looking for information on how to repair it. Seems my damage resulted from over use of bromine when my UV system was down. Anyway I found this today and while I have not tried it yet I am going to give it a shot this weekend. 

Quote

Should the interior surface develop this cellulite or pulpy surface, because you used tri-chlor compounds, you can remove this. Drain the tub and while the surfaces are still wet or damp, gently remove the pulpy material using a plastic kitchen scouring pad. Do this to all surfaces including the bottom of seats. Suck up all the loose scraped-off material, with a wet/dry shop vacuum. After you have refilled the tub, you will need to frequently check the drain strainers, since the residual pulp will collect at these locations, eventually plugging the drain holes. Also, frequently check the filter and clean and replace. After about a week the water should be clear of further fibres. If you then switch to a bromine approach or better yet a metal ion approach you can stop further fibre breakdown. You should quickly notice the beneficial effects in that the suction screen stops getting plugged with pulp.

https://www.cedartubs.com/blogger/tickets/af1c1eb4a13736d8431a107b557fed1bCedar-Tub-General-Care-Manual-Rev-13.pdf

I see your post is well over a year old so if you have any pointers since I would appreciate it.

Thanks