This tree needs to be outside where it can get the normal temperature fluctuations of the real world. Bonsai are outdoor plants and will die if kept indoors for long periods of time. Your tree is probably going into shock and reacting by going prematurely into dormancy. Elms are very forgiving and resilient. It will probably recover if you put it in a place where it gets morning sun and afternoon shade and keep it moist but not soaking wet.

Actually, I've heard stories of the ficus root systems lifting concrete driveways here in Phoenix. I intensely dislike those trees, for a number of reasons: First and foremost, they're water hogs. And if they don't get the water they want, that's when you get the wandering roots. Second, they are frost sensitive - many people ended up with dead or misshapen trees when we had the one cold night around New Years two years ago (and a particular nursery that promotes them heavily does not extend their warranty for frost). An established tree is not going to die, but you can count on having to cover it for any frost warnings for the first two winters. Third, their canopy is very dense- almost nothing will survive under it that needs sunlight - most grass will not. Fourth - these are *big* trees. Visit ASU's campus if you haven't seen a full grown one - they're right beside the ped bridge on University. They have a canopy that is 60-80' across. It'll take a few years for them to reach that size, but that's a lot of pruning that will have to be done to keep it in control, unless you have a fairly large yard. I wouldn't put it next to a pool, not only for the roots, but because it drops berry-sized fruits. Any 'evergreen' tree means that it doesn't drop all of its leaves at once, but will continue to drop them throughout the year. The Chinese Elm is an attractive tree, typically with a weeping form and interesting bark (some cultivars are called 'Lacebark Elms'). GT is right - I have no idea how it got the name evergreen. You also have to be careful about over-watering them, we lost one that was on a sprinkler watered lawn, it broke in a monsoon. These also get really tall, but not with the spread of the Ficus. Seriously, if I had a pool, I'd probably put a shade structure (pergola, patio, whatever) rather than a tree, but I know just about everyone does. Okay, enough for one night!

I'm with Mary on the chelated iron. Give it a good dose of Chelated iron, and I believe that will help. I have a Bradford Ornamental Pear in my front yard. I planted it for the red leaves it gets in fall which it does...but they dont' last very long. Knowing what I know now, 14 years later, wish I would have planted a Chinese Pistache instead. Anyway...sorry, wondering off topic. I took a can of chelated iron and springled all the way around the tree, the length of it's canopy. Before doing this the leaves were sickly yellow...amost white. Within three weeks after the application the leaves had turned a deep rich, shiney, emerald green, and it had lots of healthy new growth. It looks better this year than it has ever looked, and should provide wonderful fall red color. Easy

mylifeeclectic very valid point, Even if elms are in a mild climate they usually react to the Winter and try to force themselves into at least a partial dormancy. It's for the best, if the tree didn't go dormant it would get exhausted... as it is not meant for continual year round growth like say evergreen varieties. I would stay away from any liquid based fertilizer. However if you have a soft slow release fertilizer for bonsai add some of the little pellets to the top. I would start to address the big leaves ASAP. Elms tend to grow long shoots of leaves. Proper foliage and branch structure is maintained by cutting these shoots down to 2-3 sets of leaves. this will allow for a more full canopy and stimulate growth. It also might be time for a re potting right now in early spring. I have care guides and tutorials on how to re pot Japanese Elms (which are very similar in care to Chinese Elm) Japanese Elm Care Guide Repotting Zelkova Bonsai