What brand and model is it? What do you mean by "getting lower": flame is lower now than it used to be? and "went out": the flame went out or the flame, pilot, and all went out?. A little more detailed please.

It's a Superior fireplace. I can't find the model number. The flame doesn't go out all the time. I did some more investigating and I think it went out because the burner screen was blocked. About 2 years ago I rearranged the gas logs because one of them split in half. I don't think I arranged them properly. I just rearranged them the best I could keeping some space between the front log and the burner screen. It still seems like the flame is lower than it used to be. I also found some instructions on how ember coal chumks should be installed. The instructions came with my house when I moved in. When rearranging the logs I did not see any coal chunks. I found what looks like charred remains of the chunks. Do I need a new gas log set and/or coal chunks?

I think the best thing is for you to have a cerified tech. check this out for you, for resource and safety.