Welcome, Jennie929!
What a lucky find! These are Oncidium hybrids, and they are great house plants. They bloom multiple times per year, they are nice to look at, and they smell good. Orchids are generally easy to grow once you get the hang of paying attention to how wet the medium is, and you discipline yourself not to water when they're still wet.
If you use the Search function in the maroon bar near the top, you can search for Oncidium care and Twinkle care and read a lot more.
Oncidiums mostly need to stay moist, but don't like being waterlogged. They like to be soaked, then become almost dry. One way to tell how moist is the medium is the skewer method:
Using skewers to determine when to water
In the winter in Canada give them as much light as you can. In the summer they will like dappled sun or very bright indirect light through a window, or outdoors under a tree.
The more humidity you can give them, the better. If you have a room with lots of plants that will help. Some people use room humidifiers. Still, many people grow them without added humidity. The old advice about trays of pebbles under the plants to raise humidity does not work, so don't bother. The trays are good at keeping water off the furniture. Enough water can't passively evaporate from small trays to alter the humidity in a room unless it is tightly sealed, which is not the case for any home.
Oncidium hybrids tend to grow a new growth, bloom, then begin growing again. It is best to repot when new growth is underway. Many people repot all orchids as soon as they arrive home because the roots are often in trouble from being kept too wet, or the potting medium is old and breaking down. Other people slide the plant out of the pot to look at the roots and medium, and if they look OK, they leave it until the plant begins growing again.
When you repot, use a pot that is just slightly bigger than needed for all the roots. You might even repot into the old pot (after you clean it well) if the root system isn't huge. Orchid medium tends to break down in about 2 years, and most people repot every 2 years. Too large a pot will stay wet too long and the roots may rot.
Most people grow them in some sort of medium that permits a lot of air at the roots, like orchid bark. Some people use sphagnum moss successfully, but it is easy to keep them too wet in moss. There are many ways to grow them in terms of potting and medium; you can read about them here on Orchid Board.
Not many people pot multiple orchids together. They are frequently on different growing cycles. If a plant begins to look bad, you will want to take it out of the pot, and examine the roots. This is hard to do if they're potted together.
Orchids only need fertilizer when they are making new growth. If yours are not actively making growths, wait to fertilize until they begin. There are many ways to fertilize orchids. I prefer to use a dilute fertilizer solution at every watering during the growing season. Other people use plain water for most waterings, then a more concentrated solution once every 2-4 weeks during the summer. Water quality is important. Some tap water has many dissolved solids and this is not good for orchids. If you water leaves calcium deposits on your faucets, or white marks on windows, it is better to use collected rain or snow, or reverse osmosis purified water for your orchids.
As for fertilizer, it is best explained here:
Feeding and Watering - First Rays LLC
You didn't say what fertilizer you have. Different fertilizers have different amounts of nutrients. There are three numbers on the fertilizer label; these stand for Nitrogen, Phosphorus and Kalium (the German word for potassium.) The most important point is to think of fertilizing not in terms of full-strength or half-strength, but rather in terms of parts per million of nitrogen (PPM), which is easy to calculate from the numbers on the fertilizer label. People who fertilize at every watering use 25-75 PPM. People who fertilize monthly use 100-250 PPM. The site I gave you at the top of this paragraph has a PPM calculator to make it easy.
So, if I were you, I would slide each plant out of the pot, and look at the roots and potting medium. Healthy roots are white or light brown and not mushy. New growing tips are bright green. Oncidiums have much finer roots than many other orchids and can't stay dry very long. Dead orchid roots are dark brown and mushy, and if you pull on them the outer layer pulls off, leaving the wiry central part.
If the plant is still in flower and the roots/medium look good, I would slide it back into the pot, and water using a skewer to tell when it is dry inside. When the plant begins growing again you will have done some more reading, and it will be time to repot into the pot and medium you wish to use. Decide whether you want to fertilize at every watering during the growing season, or periodically.
If any roots look dead, cut them off. Discard the old medium. Repot into the smallest pot that will accept the injured plant. I would use medium orchid bark. Soak the bark for 6-12 hours to dampen it. Use the skewer as mentioned to decide when to water. Don't fertilize a plant with unhealthy roots. Keep the plant as humid as possible, and in the shade, because it has few or no roots, and can't take up as much water as it should. The plant will begin to grow new roots from the newest growing area. It may make a new vegetative shoot before or at the same time as it makes new roots. When it makes new roots it will begin to use more water, and you can begin fertilizing.
Many people use kelp extracts for plants with root problems. The better kelp extracts contain rooting hormones. You can find some locally at a hydroponics shop. If your plant has root trouble, when you are going to repot it, soak it in a kelp solution for 4-6 hours before potting it. Let it get dry between waterings, and use the kelp about every 1-2 weeks until new roots begin forming.
I know you can be successful. It takes a lot less time to do this stuff than it takes to read it.
Be sure and take photos and show us your plants.
Caring for Twinkle Orchids?
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