With regards to your Bonsai, I would go back to basics and confirm things like:
Placement – Are your Bonsai in the same light, wind and temperature conditions as before you purchased them. This will be difficult to tell with the trees you purchased online. (I tend to discourage purchasing Bonsai trees online because you’re not sure of the optimal conditions for that particular tree.) You may have to research online what type of sunlight conditions are best for the trees you purchased online.
Sun Light – Some trees like full sun, some partial. If you’re not sure research online as to how much sun your particular tree needs. Your photos show your trees next to the side of a building. I’m not sure if this is where they are kept, but if so you want to make sure they are getting the morning sun light.
Too much wind is one of the worst things for your Bonsai because it dries out the tree. Make sure they are not in an area that receives constant wind.
Water- Are your trees getting the correct amount of water at the correct time? Here’s a goofy little video I put together on watering your Bonsai:
http://bonsaimentor.com/bonsai-blog/88-how-to-water-your-bonsai.html
I know these may seem simple, but too many times I’ve seen situations where people see a change with their Bonsai tree and start throwing fertilizer, insect spray and other things while overlooking the basics. I myself have been guilty of this too.
With regards to your photos:
White Build Up
It’s difficult to tell, but the white build up seems like a natural occurrence from being in a damp environment that happens over time. (You see similar build up on stones). I would not worry too much about it. You could dampen it and then remove with a gentle tooth brush or other means that will not harm the bark. It’s always a good rule to attempt using physical means of removing things before spraying with chemicals.
Repotted Fukien Tea
I’m not sure when you repotted the Fukien Tea, but winter time (even though we live in Hawaii) is not a good time to repot Bonsai.
Trees have a natural occurrence of storing nutrients in their roots during the winter. When spring rolls around, the tree draws from this source to bring it out of dormancy.
By repotting, which when properly done involves removing roots, you take away these stored nutrients. When spring time rolls around the tree struggles to come out of dormancy.
I’m not sure what type of soil you used, but it does not look like Bonsai soil and I would question whether it’s getting proper drainage.
Fukien Teas are pretty hardy trees. I would just make sure it has good morning sunlight, while we still have some cool weather water it once a day before 9am.
I would not throw any fertilizer at until the new roots develop.
Once we get a 2-3 weeks more into spring, you may want to defoliate (remove) all the leaves. This may help to jump start the photo synthesis.
Anyways that my take on things. I hope it may be of some use. Just remember having Bonsai as a hobby requires patience and consistency. Doing a little each day is way more effective than doing a lot from time to time.
Let me know if I can help any further. I always like to talk about Bonsai. Also, I will post this in the forum as well. I’d be interested in any feedback from the other members.
