Doctor, please! Sick Philodendron Congo Green!

I am a real beginner green thumb, so any advice will be appreciated!

New plant, potted about six weeks ago & fertilised with Osmocote Indoor Plant Fertiliser, at that time; only in the last week have I noticed the following deterioration...
There is one leaf turning yellow, one larger leaf going soft and dark brown.
This potted indoor plant sits on my bedside table, back of my bedroom away from windows, but is close to a wall and a bedside lamp.
The yellowing leaf is the closest to the lamp.
The browning/softening leaf is closest to the wall.
You may also be able to see some other interesting marks appearing on some of the other leaves too...


I have done a little reading on:
yellow = over watering
browning = cold shock

But what do you think?!
Thank you in advance!

Hi RoseTonic, does the plant have good drainage? Personally, I would move it to another location out from under the lamp - a spot that has moderately bright natural light but no direct sun.

Hi.

I wouldn't move the plant, or change anything in its care. I would cut off both affected leaves. Anything that turns yellow will not become green again, so off it goes. The leaf with browning is interesting. The fault starts along a circular line running across the leaf. Anything between that line and the bottom end of the leaf is deteriorating, but everything above the line seems fine. I include a picture to show the area I am describing. I would say that somehow, that leaf got crushed against the pot's rim. The right side seems to have been damaged worse than the left side, but a slight mark exists on the left side, too. It's as if the leaf had been bent. I could be wrong. At any rate, I'd cut off both leaves and leave the rest alone. That's just my opinion and, as I have said, I could be wrong.

Sylvain.

Usually indoor lighting is not enough for plants. I do not keep any plants in the house under artificial light. I have quite a few in natural light near windows.
a) Artificial light has the wrong spectrum for the plants.
b) Lights are not left on long enough.
c) Lights are not bright enough.

I though the same as Sylvain about the leaves. Even more so looking at the marks on the upper right leaf in the last picture. Sure looks like the leaf got folded or compressed a bit.

Thank you all!
Perhaps the browning leaf could be a result of being "sandwiched" accidently against the bedroom wall?
You can see some interesting marks starting to appear on some of the other leaves as well.

Looks kind of like a humidity problem - notice how the affected leaves are all past the edge of the pot. Sylvain has a good point in that the plant may have had its major rib broken and cannot provide any nutrients and water past that point. I would do like he said - cut the entire leaf off or at least the damaged part. New leaves will come on as long as the root system is healthy.

I grow all my philodendrons under shoplights in winter and outdoors in summer without much fanfare so they can go from much lower light levels to full sun (acclimated of course) and do very well.

Great points - I have removed the two leaves and relocated the plant to the bathroom to see if the humidity there will help. Thanks for the advice!

hcmcdole: your plants look amazing!