Without a picture, it's hard to say. There are a few red flags in what you've written. I know culinary herb pots are a trend, but from the perspective of healthy plants, they're not really good. All three of those can become large plants and are probably overcrowded unless you're talking a very large planter. All three need a lot of light, and sunny windowsills may or may not be enough. With windows, it also depends on they type of window--many of the newer more efficient windows block much uv light that plants need. Also, those three are arid herbs that need very good drainage when grown in a pot. Rosemary and Thyme are very susceptible to root rot. It's a balance between enough water for the plant, and not too much.

balloonflower, thank you for your reply. I don't have a photo of it yet but it's in a planter that measures 6" x 6". It has good drainage. I didn't want to put it outside yet because it's still a bit chilly in my area. Thanks so much for helping me with this.

Thyme, rosemary, and sage all do best when watered lightly only when almost dry, as well.

The sage will probably become the largest first, unless you prune it by harvesting some of the leaves from time to time. The rosemary may also eventually outgrow the pot unless it also is pruned by harvesting.

Thyme usually stays relatively small.

6 inches by 6 inches is far too small for even one of those plants I'm afraid. Rosemary can grow 6 feet across, sage can cover a square yard and thyme can be a good 2 feet across. If you are in 8b all three of them can almost certainly live outdoors all year round and will be much healthier for it. Although the idea of fresh herbs in the kitchen sounds wonderful, herbs just don't like indoor life. Just outside the kitchen door would suit them far better.They need sunshine and fresh air.

I have all three of those herbs outside in pots and they survived several frosts and freezes.

I had the little pot outside when I first bought it a couple of weeks ago, then I noticed it was wilting. I phoned the store and she (the clerk) told me I should not have it outside yet because it's still too cold. Okay, I'm going to plant it in my garden outside and see what happens. Thanks everyone for all your help.

I don't know the temperature in your location - we are still getting snow and below-freezing temperatures, but I suspect zone 8 to be warmer? But anyways, just because plants can survive frosts and cold temperatures, doesn't mean that it is advisable to buy plants raised in greenhouses and move them immediately to cold, outdoor locations. It would be like taking you in shorts and a tank top from a beach in July and plopping you in your backyard in January. Ouch! There was not chance to acclimate to the temperature, wind, rain/snow, and so on. I would opt for keeping the plants indoors until the weather is starts to warm and become mild for spring -- which it could already be in your location for all I know. When you move them outdoors, they will need to be hardened off. Look that term up in google or back posts here.

FataMorgana

I agree with fatamorgana, except I'd start the hardening off now and try to get them outdoors asap.