This is going to be long and for that I apologize in advance. If you read all this and can help me, I would greatly appreciate it!

Problem 1-

I posted a few weeks ago about my new plants that I aquired after my father-in-law passed away. The only plant I owned prior to this is an ivy, so I'm learning as I go. I think my Dieffenbachia has a bacteria infection in it's stem. When the funeral home brought it to us, they set it on top of a freezer and the wind knocked it off causing one of the main stems to break off. It healed over like a scab, so I didn't do anything to it. I repotted all the plants because they were severely root bound in their pots after I posted for information. A couple of days ago, I noticed that the stem below where it broke, is now soft and slimy. I didn't do anything to it immediately because I didn't know what it was. After looking online the past couple of days, I'm thinking it's a bacterial infection and isn't easily treated. At first, I had a problem with this plant's leaves turning brown and I thought it was sunburn from putting it on my porch. I cut all of the brown leaves off and it grew new growth and was starting to look as good as when I got it. Now I have this problem and I'm wondering if the two are connected. I've been using a water meter because I'm scared I'm going to over water them. I didn't sterelize it before I put it in the other plants because it never occured to me that I needed to. I check them daily. I even check them all today before I pinpointed the problem. Since this infection is very contagious, did I just infect all my other plants with this meter. What do I do now?

Problem 2-

I also received in the mix of plants 2 cyclamen. At first they were growing very well. Over the past week and half one of them started going down hill quickly. I thought maybe it was root rot because I've been watering them from the top, not the bottom. I've since bought a few books on plants and now know I messed up. Anyway, I decided to take it out of it's pot to examine the roots and I found these tiny shiny bugs on the bulb. If they hadn't shined in the light, I never would have seen them. At this point, it only had 2 leaves left on it. After searching online, I think they are cyclamen mites. I found a site that said to soak it the plant in hot water and it will kill them without hurting the plant. I did this tonight and now I have no leaves at all because they just fell off. I don't however see anymore mites. Do I repot the bulb or is it too late?

I'm now scared I'm going to lose all my plants to either mites or bacterial infections. I'm so sad right now because I wanted to keep these for sentimental reasons.