Welcome to SKF Aquatics ... let's see about your question.
Firstly, your tank is still in the cycling phase, as you mentioned above. During this phase, a warm temp is required for the growth of the beneficial bacteria. You want this at 80-81 degF. Using Danios to assist in cycling a tank is not a good idea, because they prefer cooler temps (65 - 76 degF). You'll never get the tank warm enough for good BB growth -> Cycling will take much longer. It will still cycle, but it takes longer. Of course, that assumes there are BB present in the tank. If it is not added from another source, then cycling will take even longer.
Second, assuming your tank has now been cycled, and you are not reading any Ammonia or Nitrites, you can reduce your temps for the shrimp to 71 - 75 degF (22-24degC). So a fluctuating 68-72 is better than a steady 78 any day. Shrimps don't have a problem with the cold, it's the heat above 78F / 25C that they don't like.