Ok i had an Eureka moment and i think i know what happened to ur plant. What did u do with the mold when u reppoted it?U either try to remove ir wich u may have succeded or u leave it there, well if u removed it partially or if u let it the remains hold water, so in the middle of the pot is a mix of soil with spagnum mosh that dries fast, in the bottom rocks that stop the root system to develop downwards as it should do, and in the top u got mold covered with soil that dries slower since the root system is not on the top, so u check the top soil for moisture and u water it when the top is dried up, but the thing is where the root at were dried up way before the top were, and the plant tried to develop new roots to reach the plate where the water is but couldnt but i didnt realize this because the top looked moist, or moistfull enough for ur taste(actually in the pictures looks too dry for peace lilly).Take out the rocks, if ur going to repot dont do it in anything smaller, now the root system is probably looking to grow so dont downgrade it to a smaller pot, and water the plant.

Im not sure if i made myself clear, but if i didnt i may try to explain myself better.Just english is not my first lenguage.