it's a bit diffacult to give you an answer that will cover all your Orchids untill you tell us what all of them are. The one thing I can say that should help with all of them is more light. Light is so important to orchids. they can grow just fine with less than ideal light but they rarely bloom with out enough light. Also some Orchids require changes in day length, some it's temperature drops,and for most its's a matter of waiting for a new growth to mature as well. If you have low light Orchids you might be giving them enough with your exposure but for the medium to high light orchids you need to supplament the light they are getting with a man-made light source. I suggest getting some Compact Florescents and adding them to your growing area. If you will look back through older posts you will find many posts about light for Orchids. With out getting into too much repeat detail It is very diffacult to get enough light from a window unless you have perfect windows with no obstructions and you only grow low light plants. Look back through the posts and pay very close attention to posts and replies by a man named Howard. Howard is the Light GURU and what he says is worth reading.

Increase the light level before worrying about any other factor. It sounds as if you have many parts of the puzzle in place so a little more light might well bring you flowers.

One general bit of advice: Patience! 6 months is generally not long enough to own a plant and expect it to bloom for you. I didn't see my first orchid rebloom until a year and a half after I bought it, and I suspect thats the case for a lot of people here.

To help you farther, we DO need to know what kind of orchids you are trying to grow. Please fill in that blank :) How do you have them situated that in a SW window they are only getting indirect sunlight? Is it obstructed in any way? In my SW window my plants get a few hours of direct sunlight. If your light is only indirect, that could be your problem. A SW window should have sufficient light for everything from phal to cattleya (NOT high light vandaceous types), in my experience. Light isn't the only reason, a lot of plants require a winter rest of one form or other. it all depends on what plants you're trying to grow.

Lush green leaves are not what you want to see on an orchid if you want it to bloom. Light olive leaves are best. More light will help that. Also, fertilizing with too much nitrogen tells the plant to grow leaves, less nitrogen tells the plant to bloom. If you use a fertilzer high in nitrogen, you might consider switching to a lower nitrogen type.

THANK YOU ALL for the excellent advice! Since most of my orchids were given to me from people who didn't want to take care of them :( I don't know the varieties, but I'll look up as many as I can (from what I remember of the blooms) and post back here when I find the names. Again, I really appreciate your time and suggestions! Gratefully, Lindsey :)

If you can post pics of your orchids many of the folks here will be happy to help you ID them. It will be almost impossible to give an exact id but we can help with species which will go along way in knowing the gowing conditions.

Type of plant can make a BIG difference! Some bloom in response to lower growing temperatures, some to changes in day length, some time it to coincide with emergence- or maturation of new growths, and some just bloom when they feel like it.

I think the patience recommendation is a good one, but keep in mind that generally, there are three factors that reduce/stop blooming in orchids:

Insufficient light
Insufficient nutrition
Too much nitrogen (such as Mir-Acid 30-10-10)