Soil fungal infection, help wanted please

Hello everyone, we're new here and would like some help and advice please.  

My wife and I are veg patch novices who have just started to try to grow some vegetables in our little patch in the garden. The patch is a raised bed contained by oak sleepers, which were put in 3 or 4 years ago. The veg patch is around 4 by 5 meters. A while after the sleepers were fitted we noticed that some of them had a thick white, rubber like fungus growing on them. At the time we scraped it off and thought nothing more about it. However, having recently dug it over it looks like the affected sleepers have severely rotted, to the point that they'll soon need replacing.  

We also noticed a white, tissue like fungus in the soil, see the attached pictures. Are these 2 fungi (assuming they are fungal infections?) related? Is the soil fungus likely to cause any problems to us growing anything (there's currently some rhubarb and strawberries growing in the patch and they seem to be growing well) but could the fungus affect anything else? If it turns out that the fungus is nasty, what's the best way to treat the soil to eradicate it?  

We grew some potatoes in the patch a couple of years ago but we obviously hadn't harvested all of these as we have since dug up a few odd ones, some of which are partially rotten, could these have cause the soil fungus? 

Any help and words of wisdom greatly appreciated, thank you.