That is normal. Each flower has a limited life span.

I don't think so..Even New flowers are turning black ... the stems are Yellow!

Hey sonic_blu, I am having the same problem with my peace lily. Leaves are completely healthy, but the flowers are turning black even the newly sprouted ones. Did you ever figure out the issue?

It may be from overwatering. http://www.flowershopnetwork.com/blog/peace-lily-spadix-black/

Did anyone solve this mystery?
I have the same problem and don’t think it’s an overwatering/under watering issue. This is something else. I checked the roots- roots are healthy.

That roots aren't dead should not be taken as indication they are functioning normally. Too much water in the grow medium limits the root's oxygen supply and thereby limits root function whether or not the soggy conditions open the door to a rot-causing fungal infection.

Many growers reason incorrectly that because PLs are often found in riparian (waterside) settings, it must follow that they like or prefer a wet or boggy grow medium. This is not the case. Roots of PLs adapt easily to any of several forms of water culture, but during that adaptation the root structure morphs to allow air from above the waterline to diffuse through root tissues in order to provide oxygen to burn the fuel (food/ carbohydrate/ sugar) that powers the metabolic function of roots. So instead of roots being filled with parenchymous tissues common to terrestrial plants, aquatic plants or those adapted to some form of water culture will be filled with the airy tissue aerenchyma. This means roots are unable to make the rapid (for plants) and endless cyclic of transitioning from too much water in the medium to an appropriate amount when their care giver has a hand too heavy on the watering can.

Misting, thrips, over/under-watering, and a high level of dissolved solids (salts) in the soil solution can cause the symptoms shown in the OP.

Al

Thanks for the details. It’s very helpful. I watered exactly 250ml bottle of water every two weeks throughout winter. Now in summer I’m watering every Sunday.
The only difference is, I started using tap water exactly 3 weeks back. That’s when I started noticing the problem. Probably it’s the water. Will switch to distilled water. Does it like plant food (Miracle Grow)?

The most skilled growers either water on an as-needed basis (as opposed to a schedule), or, they use a very well-aerated medium that's fast draining. The media I use drain so fast/thoroughly I would be hard-pressed to over-water anything,

The tidbit about having changed your water source could be important, particularly so if your tapwater supply plumbing is routed through an ion-exchange water softener? If so, using it will be a significant and compound problem, the 'compound' parts would be a very high TDS (total dissolved solids/ salts) level and toxic levels of NaCl.

If you're shopping for a fertilizer, let me suggest Dyna-Gro's Foliage-Pro 9-3-6 as your 'go to' product for containerized plants. It has ALL nutrients essential to normal growth (few fertilizer products can make that claim) in a single package and nutrients are provided in a ratio the plant will appreciate.

Another plus is, its nitrogen is not sourced from urea, which helps to keep plants full and more compact. You'll likely need to order it online.

Al