Shiitake requires high humidity at first (over 90%!). Once the mushroom pins form, reduce the humidity to 70%. Make sure that it is very humid inside the humidity tent for the first few days. Remove the humidity tent once the mushrooms are almost full grown (or if the tent no longer fits over the block)

The brown spots on the block are normal. The block will turn almost totally brown before it is ready to produce

Shiitake can be temperamental. Be patient with your block and ensure it’s getting light, moisture & fresh air. Use clean utensils for harvesting, to prevent contamination.