Afraid I can't send picture as don't know how!
I assume that you have access to a digital camera as you did not say otherwise. Go to this site [url]https://imageshack.us/[/url] Browse to the location on your computer where the picture resides and click "host it". Then choose the appropriate link, (thumbnail for forums will do ), then copy it and paste here.
The leaves start off light green and turn darker (but they are all falling off at the moment) they are mostly toothed or forked at the end.
It does not sound like an Elm to me, Elm leaves are serrated, (toothed), all the way to the leaf stem.
It had lots of little single white flowers all summer
Did the flowers look like this? [url]https://www.wafu.com/dictionary/az-900.htm[/url]
hubby says its probably losing leaves cause its autumn!
If it is a tropical it is not losing its leaves due to the change of season, you are doing something it doesn't like. A lot of problems with commercial bonsai can be traced to poor soil.
Read this: [url]https://www.helpfulgardener.com/forum/viewtopic.php?t=3422&sid=c74c8b18edc9dc782c675056125b49a6[/url]
And this: [url]https://www.helpfulgardener.com/forum/viewtopic.php?t=3530&sid=c74c8b18edc9dc782c675056125b49a6[/url]
Poor watering practices may also be a factor. Let the soil dry a bit between waterings then water well.
I'm not real big on tropicals and am somewhat out of my element. See if you can get a picture up, an ID is essential. Hopefully someone else can be of more help.
EDIT: Sorry I misread the subject line. I thought you wrote "tropical"