Rick - remember me? I sent you the White Sprite sinningias. Do you remember the type of soil that was used packing the tubers sent to you? That is what I grow my micro mini sins in, it is a fine grade germination mix from Fafard and sinningia do very well in it. Keep it simple, no need for exotic soil mixes to grow these guys. Use a fine textured soil mix - really don't think you need to go to the extent of chopped long fibered sphagnum, etc.
You know that mini sins grow, bloom and then want to go dormant, right? Your plants may just need a rest, let them dry out and sit dry for a month or so, then spray them down with water to see if they will sprout and grow again. The dry foliage needs to be cleaned off during dormancy, sometimes they will signal you with green that they want to get back to growing after being dry and dormant for a period without first giving them H20 - it sounds from your description that your plants are going through their normal cycle and it isn't anything to be overly concerned about.
Here is a picture of my S. pusilla growing in Fafard germination mix right out of the bag. I DIDN'T need to stand on my head and pee into my pocket to get these to grow well and neither should you. Good luck with your sinningias!

Beautifully grown, Jeb! I've been pining for some of the Sinn. micro mini species to try out in my terrs. Many plants like the mini AVs just get too big.

Thank you for the nice compliment. Dave's Violets or Kartuz Greenhouses grow and sell Sinningia pusilla. Give them a try.