I agree about reading the sticky thread, that will be really helpful.
Also, the most common reason why people kill houseplants is overwatering, so that would be the first thing I would check on with your plants. You can't judge whether it needs to be watered just by looking at the top of the soil--it can look dry while down an inch or two where the plant's roots are will still be sopping wet. You need to wait until it's drying out down lower where the roots are before you water again. Also if your plants have saucers under them to catch excess water, you need to empty those saucers promptly, don't let the plant sit there in a dish of water. And also make sure your pots have drainage holes--some of the ones you buy come in pretty decorative pots with no drainage which almost guarantees you'll overwater them.
I'm reading through the sticky, especially about buying better soil. I'm wondering, however, if I need to repot after putting the purchased plants in better soil. And if so, should I continue to repot every year?
BUYING better soil is going to be difficult. You may need to take on the challenge of making your own, if you're up for it. If you're willing to do a little homework, I can help you better understand soils and the soil/water relationship and how important that is to your plants' health, as well as how to put together a good nutritional supplementation program (easy). If you gain an understanding of those two things, and can get your plant in the right light, you have 90% of what you need to become an accomplished grower.
If you'll put some effort in acquiring a little knowledge instead of relying on being bit on the butt by your mistakes (that's what experience is) as your principle schooling, you'll find yourself moving forward much faster than you could possibly anticipate. I'm speaking from experience and as a former failure who was simply determined to broaden my knowledge base and 'make good'.
Just an observation...the stem on the right seems to be attempting to put out new growth. If it were mine, I would clip it just above that, then follow Al's advice. An education is a better teacher than trial and error.
Just a note of encouragement. My first plant was a cactus and I killed it. . . and many more before I realized a little knowledge goes a long way.
When people tell me I have a green thumb I tell them not really I do a lot of research. You're off to a good start looking for advice here on Dave's garden.
I always use a bagged potting soil and then mix in perlite to lighten the mix. That way it's harder to over water as the excess drains out.
Also a good house plant fertilizer, either one that you sprinkle on the soil or one you add to your watering can, I like the later.
There are some good books on "easy" houseplants and "low light" plants. Start with the easy ones, there are a lot of them out there to choose from. My best looking and easiest houseplant is a pepperomia. It's gotten huge and all I ever do is water it with fertilizer water.
Your plant (appears to be Dracaena marginata) will do better and the red edges will get brighter with more light. Marginata's leaves are narrower that many dracs, but it could have fuller growth (leaves closer together).
Agree with kwanjin. There is new growth on the right plant. Cut the stem off above the new growth. Cut again further up the stem where the brown/dead part starts to turn green again and repot that piece. Toss the dead middle.
When ever one buys any plant from a big box store you should bring it home and soak it in tepid water for several hours to rehydrate the core. Some disinterested person has undoubtedly been waving a water source over the plants in the store and not seeing to it that the water actually soaks into the dirt rather than just running off. Then put it in new potting mix.
We've all killed out fair share of plants, but as said above "that's how we learn". At least you chose to ask the right questions at a good place. barb