Hi Salem, and welcome to ATP.
Yes, your umbrella plant looks like it has some mites. A very mild soapy water spray will take care of that - 1/2tsp. dish soap to a liter of water, or less. More is not better with soap. Spray every part of the plant, being sure to hit the undersides of the leaves and also the surface of the soil. You will need to do this twice, a week or so apart, because the spray kills live insects but not the eggs, so you need the second application to get the next generation before they reproduce. Then keep an eagle eye on it (magnifier helps) for any recurrence. Between applications, if you can take it outside, or into the shower, or kitchen sink and rinse it thoroughly with tepid water it will be happy.
Only other problem I see is your adenium really needs drainage desperately, so a salad bowl is a death trap. Hurry to the garden store and get a nice pot with lots of holes, and some coarse potting mix like cactus mix to lighten up that nice dark soil it's in.
Yes on the fertilizer, but I would mix it at half the strength that the directions on the package say. In warmer weather, if you take your plants outside they can probably use full strength, but right now with the new growth and cool weather, they are just starting to grow again. Half strength will be plenty.
