Clay and Peter - Both of your suggestions were really helpful!  I'll have to look into tabling and/or a tempering machine, and see how things improve.  Much appreciated!

This is absolutely the first place to start.

If you are not adding already tempered chocolate you are not properly seeding as there are no proper seed crystals in the chocolate you're adding. It sounds like you might be using a machine like a chocovision. What I would experiment with is using the "mode 2" tempering setting, which is slower than #1. Heat the chocolate up and then do not add any more during the cooling down cycle. After cooling, let the temperature warm up and after the machine says the chocolate is ready, wait for 5-10 minutes to ensure even mixing.

The #2 program is sometimes used by small makers who do not add cocoa butter to their chocolate and don't have seed. The extra time, apparently, makes up for those deficiencies and enables enough of the right kind of crystals to form during cooling. 

--
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
@DiscoverChoc

Hi,

The seeding method for tempering works only if the cold chocolate you add has already been tempered (which means that cocoa butter it contains is already crystalised in correct crystal form).

If you use cold "chocolate" that has been made and than just cooled it will not work.

If you are working with small quantities you will need to learn how to temper chocolate on table or use one of the machines which generate seed from cocoa butter.

I make dark chocolate at home from raw ingredients, and am struggling with getting the tempering right for the bars I make.  I use the seeding method for tempering.  I heat about 75% of the chocolate (including cacao, sugar, spices, etc.) to about 118F, add in the remaining cacao, cool to about 89F, and then pour into the molds.  After a few minutes of letting the bars settle, I put them in a covered Pyrex container, and then in the fridge. 

The room temperature of my kitchen is probably around 75F.

After reading some of the other posts on the forum, I think the problem is mostly due to cooling the bars in the fridge.  However, I'm also wondering if I need to change anything in terms of when I add other ingredients, the temperature of my kitchen, or the heating and cooling process.

Thoughts/suggestions?