My hostas have gone yellow , any idea why?
Certified GKH Gardening Expert
This sounds like a nitrogen deficiency. You will need an all-purpose fertilizer to apply to the area. Dolomitic lime would be good to add to keep the pH stable, as well as give the plants calcium and magnesium.
Here is a link that will help: https://www.gardeningknowhow.com/ornamental/foliage/hosta/growing-hosta-plants.htm