Marantas defintely go into a state of semi-dormancy each winter. When that occurs, you must allow the soil to approach dryness between controlled waterings. Soil should be kept evenly moist during the remainder of the year when the plant is in its active growth cycle. With this plant, it's VERY important to withhold ALL fertilizer during that period of semi-dormancy. There are some plants that have an adverse reaction to water that is heavily treated with floride, and (based on my experience) I happen to think Maranta is one of them. If your water is heavily treated, allow it to set in an open container for 24 hrs (at a minimum) before watering your Maranta. Because I believe Marantas to have an adverse reaction to floride, I prepare a soil mix for them that does NOT contain perlite. I'm linking to a U of Florida site that may be helpful. (Pay special attention to the section titled 'Physiological Problems'.) The site exists primarily for commercial growers of foliage plants, but I refer to it often when I need really helpful assistance. If you explore the site, you'll find good info on lots of house plants. Here is a link that might be useful: Maranta Info

It's hard to see anything with your white pebbles used as top dressing. I would remove all the pebbles (permanently, in fact) and make sure your plants are in a fast draining mix, preferably with few or no organic components. Top dressing is pretty but it keeps moisture IN. Cactus and succulent plants don't need that so much. It's hard to tell, but your pots do look like plastic. If you have succulents in plastic pots with top dressing, you are keeping a lot of moisture in that mix, regardless of what it is, and that's not favorable for the kind of plants you have.

Pv4291, when you are designing a succulent arrangement that will last more than a month, the best you can do is to play with the form and color of the plants, the pot and rock cover. Like this: You get the idea. Follow some simple rules: 1) Draining holes is a MUST HAVE 2) They need a fast draining soil, specially if your country is cold/have the four seasons 3) Preferiblely, use terracota pots. Personaly, I think that painted terracota is ok too. 4) Agrupate succulents and cactus with similar needs of light, watering and fertilization 5) Place them where they can get enough sunlight so they will conserve their form for longer and get those pretty red and pink shades. If you have a guest you can move them for decorative reasons for a couple of days, and then put them back in their place. Basically, think what do you want, do your search to see what would be the best plants for it and what they need to be happy and healthy and look fabulous in your design

It's not unusual for some plants to lose some leaves after you bring them home, they're often adjusting from brighter light conditions to lower light. He actually looks pretty healthy to me but ,certainly, if he needs a bigger pot you should def repot. I would move it closer to the window if possible and let him get a bit dry (about 1 or 2 inches deep) before watering. He should push out some new foliage soon that's more adapted to your light conditions and you can always cut a few of the longer branches and root them in water to make the plant more compact and bushy if you want.