Hermit crabs are pretty resilient as marine animals go. Of course, what extremes can be tolerated varies from one species to another, but your Clibanarius tricolor are pretty darned hardy when it comes to ammonia/nitrite/nitrate spikes. But, a spike of 20ppm is a lot less serious than a spike of 40ppm or more. What level are you getting?
They don't do much often unless I put pellets in then they go off on a hunt for them. I guess them being lazy most of the time is normal?
That's normal when the crabs are well-fed. If would be safe to let them fast for a few days if the salt will arrive soon. There may be some things hidden in there that are contributing to the waste spikes. Also, do you see the hermits eat all of the food you've added? If you see one go off some place sneaky with a bit of food and then return shortly after looking for more, then they may be stashing it. Food caching is another thing that can be solved by a few days of fasting.