I have a large unknown plant in a pot that gets AM sun on my front porch. I got cuttings from a plant growing in a pot right on the beach in So.Fla. Thought I must be able to grow this! Grow it did! It has pale green waxy but soft leaves but has no flower. Suddenly there is a hard white crust growing on the soil (Miracle Grow Potting Soil) and the plant is dying. It is actually rotting and turning slimey. I am not watering too much. This plant lived on the beach in very dry conditions. I have a second of this plant on the back screened in porch and it is fine. What to do?? Wish I had a picture but I cannot do such things on a computer.
Pictures would really help if you can find a way to borrow a camera. Rotting and turning slimy tells me that even though you think you're not watering too much, you are. You could also have really poor draining soil in your pot which would make it nearly impossible to water properly, but either way those symptoms say too much moisture to me. The white crust is probably salt buildup (from fertilizer or hard water) and is not likely the root cause of your problems.
If you can't post a picture, it would help if you can describe a little more about the pot & plant--how big is the pot relative to the plant, does it have drainage holes, if it has a saucer under it to catch excess water are you emptying that promptly after watering, what type of soil/potting mix did you use, how often are you watering, etc.