I also got a Marginata not sure if I need to replant it as well. It is currently 8-10 inches. What size pots should I get for them?
If you wanted to put them in a more decorative outer container you could do that, just get them a little larger than the pots they are in.
If you want to repot, be sure to only go up a size or two in pot width; too large of a pot is detrimental. You really don't need to unless the plant is rootbound or seems too big for its current container. Get to know your plants. Some perform better when rootbound.
https://www.gardeningknowhow.com/houseplants/hpgen/learn-more-about-repotting-houseplants.htm
What is the name of the taller plant, how much and how often do I water it? Fertilize it? We have two sets of these. They are in an office lobby, indirect light. Thanks so much!
That is called a "Corn Plant" or "Corn Palm" (Dracaena Fragrans).
This article will help: https://www.gardeningknowhow.com/houseplants/dracaena/how-to-grow-dracaena-corn-plant.htm
I have a dracaena plant I am repotting as the leaves started turning yellow. I found it had become rootbound and needed a bigger pot. Should I continue with the regular potting soild I used before?
You can use any well-draining potting soil for houseplants.
https://www.gardeningknowhow.com/houseplants/dracaena/dracaena-houseplant-care.htm
The red dots happen even on the new sprout leaves.
It likely has been overwatered. This will lead to what you see here. This bacterial blotch is quite aggressive, and will likely never go away completely.
You can control it, but eventually it will kill off the plant.
Control includes antifungal agents, and cutting off any HEAVILY affected growth. Cutting off too much at once will kill the plant, as well, so it is important to only cut it off once it is too unhealthy to photosynthesize.
This article will offer more information: https://www.gardeningknowhow.com/houseplants/hpgen/desperate-houseplants-dealing-with-common-houseplant-diseases.htm
Should I do pruning, or should I cut the stem?
That is on its way out! There will be no saving this one. These should never be planted in clay soil.
Unfortunately, you will need to start over with a fresh tree, and care for it with the proper soil, water, and light requirements.
This article will help you to care for Dracaena: https://www.gardeningknowhow.com/houseplants/dracaena/dracaena-houseplant-care.htm
Tree is about 4'6 and in a pot.
Yes, your 'Dragon Tree' can live outside in summer while there is no danger of frost.
https://www.gardeningknowhow.com/houseplants/dracaena/dragon-tree-plant-care.htm
I had a Dracaena Green Jewel that was getting to be about 2' tall and was about 11 years old. I decided to cut it down. The rooted top picture is of the top that I rooted and then transplanted into a pot. Not sure what is happening, as you can see the base of the leaves are turning brown. What am I doing wrong? Rooted stem picture is of a section of the stem that I rooted and transplanted. It has been 5-6 weeks since I transplanted, but no shoots are growing yet. Is this common, or is there something else I should have done? Original picture is of the original plant, seems to be doing fine. What are the little growths at the base of the plant?
Do you know what type of soil that you used for this? The soil should not contain many nutrients at this point. These are not heavy feeders anyway. Certain soil, such as MiracleGro and others with fertilizer can cause burning and rotting of new shoots. If these are already rooted, then these can recover over time. Just be careful not to over water. Next time use a product marked as a seedling mix or soilless mix.
This collection of articles will help you to care for these: https://www.gardeningknowhow.com/houseplants/dracaena