Minh,
I can positively identify one of your problems, scale insects, on the top leaves/stems of your second picture. Those are the black oval buggers that satisfyingly crunch when smooshed.
I am also pretty sure you have a spider mite infestation, based on how your leaves look. I could be wrong though.
I had similar looking scale insects on my indoor citrus, which I finally managed to eradicate with horticultural and dormant spray oil (I use Bonide). This should take care of your mites too (spray three times over about ten days).
The biggest problem that I see is how to work around your blooms. The Bonide oil produced no negative reactions in my plants, but I’d hate to have all your delicate flowers drop off as a result. Maybe if you don’t have huge areas to cover, you’ll be able to avoid the flowers if you spray.
Insect killing soap (Safer, etc.) would probably work as well. I recommend using real soap intended as an insecticide, and not the DIY dishsoap et al. remedies.
Good luck!
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Lack of fertilizer
I use BONIDE but all my flowers drop like crazy …
What’s you mean lake of fertilizer?
@Minh, read “lack” as “not enough of” or “in need of” instead of “lake”, as in a large body of water. 
M
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