Perhaps you live in Western Washington like I do as my lily of the valley bulbs also had very few blooms after years of flowering. Either overcrowding, very dry weather or even underground root damage due to voles or moles could be the problem.  I suggest you let the pips or bulbs lie dormant this summer which means they do not need extra water. Then in the spring you can apply a slow release plant food like Osmocote to the soil and see if this helps. A covering of weed free mulch such as leaf mold or washed dairy manure or even bagged compost will enrich the soil and help boost the bud production on the plants. A mulch will also help to protect the plants from drying out in the late spring when flowers are produced. I do think next spring will be a much better year for these fragrant plants. Keep growing, Marianne Binetti