Lotus buds don't open

Any reason my dwarf lotus would make lovely buds that get big and fat but don't ever open, then all the petals drop? That's what happened to the first two buds so far. There are more to come so if this is a known problem that has a solution, I'd really appreciate help.
Many thanks!
Deb

Update: this morning I spotted a bud that had opened but it was below all the aerial leaves.

This plant gets a minimum 7 hours full sun. Day temps in the 85-95F range and avg humidity around 15-18%. It's a dwarf and is in a large, deep tub with the water line about 4-5" above the soil. When the water gets too low, I sometimes top it up with rainwater that is the same temp as in the tub. Tons of healthy-looking leaves.

Thanks again for any insight you can give. :)
Deb

This is the latest "not to open". :(

Deb, that has happened to me for two years in a row so I gave up and do not have any lotus this year for the first time in ages. I wonder if there isn't some mite or something that is getting in and distorting the buds.

I even tossed the old plants that had performed so well over the years and bought a new one a year or so ago and when it happened to that one too I contacted the grower, Perry's Water Garden in NC, and they had no ideas about what could be happening. Be interesting to know what is going on.

Thanks, A.
Perry's is where I got mine and I was considering calling them, but guess that won't help. Another bud finally opened yesterday but it was obviously well past the day it should have. The petals were already dropping.

I wondered about some sort of insect, too and then I read that you should avoid using any pesticides on Lotus, so I have no idea what's to do.

Thanks for the info. There are plenty more buds, so I'll just wait and see. If it keeps happening, I may try a tiny bit of malathion.

Interesting that you got yours at the same place. What variety is yours? Offhand I can't remember what mine was but I might recognize the name.

There are applications for water plants. One is called Liquid Lady Bug.

Thanks, Mary!