I know this is ages out of date, but there is no way a little bit of fungus, or even a scratched element, will contribute to softness. At best (worst) these things, in massive amounts, will cause contrast to drop a bit.
I actually started using a Rodagon 80mm f.4 two days ago, and mine is a very beat-up example - scratched, bit of fungus, the works - but it's still the best lens I've used thus far for enlarging 35mm negatives. I much prefer the extra working distance, and don't do huge prints.
It is visibly superior (resolution, shadow/highlight rendering a.k.a. contrast) to the El-Nikkor 50mm I was using. Soft images must point to focus error, or enlarger head mis-alignment, or (if you didn;t test with nother enlarger lens) a soft negative to begin with.