Soggy lily flower buds

HI all. I have a problem with my water lilies. Got a couple of pretty
flower heads but I also had several mushy flower buds that just were
floppy in the water. The plants along with soil, rocks and water are in
a large plastic container which I put them in early last year and I had
the problem last summer too. Don't know where I'm going wrong. Also seem
to have loads of lily pads which cover any pretty flowers so I am
removing some of the pads so I can see them. Also have some of that
green slimey blanket weed which I remove every other day. Would
appreciate any advice, thank you.




--
Lintama