Honestly, your plants look pretty good to me, although what you are describing with the bottom leaves sounds like a water issue. Generally, when this happens, it means you are watering too much or the soil you are using retains too much water. I would first suggest not using a potting mix straight out of the bag; the easiest thing to do is use half cactus potting mix and half perlite or pumice, although you will find many recommendations for more complex gritty mixes on this forum. What you are describing with the leaves spreading out sounds like etiolation, meaning the plant is not getting enough sun. However, I don't really see evidence of this in your photo. If you are worried, though, you can move the plants to a sunnier spot. If they are in the shade, do this slowly over a few days to avoid sunburn. The plant you are talking about is E. 'Perle von Nurnberg' and the leaves towards the center will always be brighter in color, turning more greenish as you move outwards. I'll attach a picture of how the plant should look, very similar to yours.

Here is a pic of the new growth. I'm assuming the black was rot. I really don't think it started to rot until I watered it, but maybe I just didn't notice it. It's with the other non-cacti now getting lots of fresh air and light, but in the same pot from the store. It actually has a name on the pot instead of Echeveria sp.--it's E. agavoides, it has a long way to go to look as beautiful as the pictures I see online.

Samantha I don't think if you should water more often (I suggested: ...don't rush watering more often...). While keeping them too dry is not advised, underwatered plants usually recover easier than overwatered. They could be dying off because of the condition plant was in before you got it, I was just thinking that plant may have recovered in 4 months. New leaves look quite good. Checking the soil deep inside of pot would help. You can use bamboo skewer or chopstick, insert deep (at least 3/4 deep) into soil and leave there for few minutes. When you pull it out and it is dry & clean, time to water. If it comes out cold and damp and may have some small particles sticking to it, do not water - there is still enough moisture. IMO, I would not put more soil around the stem - there is better air circulation around it this way. I would wait until I was sure there isn't any problem. Eventually, you could put some grit or small stones on surface if you don't want to see the stem.

Al Tapla would you be able to tell me what is wrong with mine? I've had this tree four four years and never had any trouble with it but now I am killing it! I wanted it to grow more branches so I pruned it and moved it to a sunny-er spot and added grow lights and started fertilizing more regularly. Next thing I know, it's getting yellow blotches all over the leaves and sometimes red speckles and tiny pin holes. I found spider mites on a different plant, but I couldn't see any on this one, but I hosed it off and sprayed with dish soap in case it was mites. Then the soil was soaked and wouldn't dry and a week and a half later this leaf turned black and dry in the center. I thought maybe it was because the soil was wet too long. I freaked out, so just yesterday I did a full repot (never done this before) and added perlite and orchid bark mix to potting mix to get a grittier faster drying mix. I also cut off half of the leaves. It really doesn't look too happy today (droopy leaves and soft stems and even more red speckling on new leaves) I don't know if it's been given too much light, too much fertilizer, too much water, or is infected with mites, or all of the above. Anything you can suggest? The tiny pin-holes make me think mites are one the table but I hate to stress it out more if it's not that.