Does the pot have good drainage? And what's the soil like?

I suspect one of two issues: drainage/overwatering, or possibly nitrogen deficiency. Nitrogen deficiency tends to produce yellowing margins that don't have a distinct pattern. Yellowing begins in the oldest leaves first. Poor drainage and/or overwatering often produces a blotchy effect, sometimes creating necrotic patches, but it can also cause an overall yellowing. I'm not sure why it presents differently at different times or in different plants, but I suspect it is because some roots are more affected than others, so the parts of the plant fed by those roots show damage first.

Fertilizing a plant that is sick due to something other than fertilizer deficiency will cause worse problems, so your best bet is to dig into the pot and determine whether the soil and roots are healthy and not crowded or soggy.

This is definitely not nitrogen deficiency. It looks like a water problem.

well well guys ,

it almost all of you agree about a water and drainage problem

but I'm sure the yellowish spots start appearing before I moved the
growing pot into the white pot ( which I thought it has poor drainage ) .. what I mean that month ago the plant should have a very good drainage which was the time I took the pics above ..

maybe it's over-watering ? but I check the first inch of the soil every time before watering to be sure it's dry : L

what should I do now ? do I have to check the root system ? decrease the time between watering ?

maybe it about how much I water ? it's quit a large plant to me( look at the tissue box beside it ) ..and I water it thoroughly , is this too much ?

here a pic of the soil and there are some weird stuff on bottom stems

I'm just a beginner at these stuff

It's making aerial roots, perfectly normal.

In the pics, it looks like the soil is moist in the middle, but not thoroughly to the edges. When you water, do it so that all of the soil is moist, then when it quits dripping, it can go back in the outer pot. With plants that don't appreciate drying out, like Philos, it's even more important to have a porous soil mix so that the constant moisture doesn't cause rotting from lack of oxygen. Oxygen + moisture = healthy roots. Moisture + no oxygen = rotting/suffocation. Oxygen + no moisture = shriveling & death. Unless something mechanical has happened to a leaf, compromised foliage is a sign of compromised roots. I would be considering repotting.

when you asked about the pot drainage I thought I'll be " over-watering problem "

I'm thinking of something when you said " mechanical " , it's a spray the gardener gave me to keep the leaves clean and shiny

it dose keep my plants shiny .. but many of them not in good condition too ..

IMO, being clean & healthy is all the shine a leaf needs. Some are naturally more shiny than others.

Give your plants an occassional shower and wipe the leaves with a soft cloth. They will look just as happy as if you used an artificial leaf shine.

This definitely looks like bacterial infection I got on my imperial red. It kept increasing in area and started on other leaves until I cut the affected areas/ leaves.

Hi, I know everyone says it's overwatering because it's the most common reason for a sick plant, but I have this type of philodendron too, and same thing happened. The leaves got brownish and yellow all around the leaves and became much thinner.

For me, it was a bacterial issue.

If it's not too late for your plant or for other people reading this, here's how to fix the issue.

- cut off the sick parts of your leaves.

- with a clean rag dipped in lemon water, wipe the cut edge of the leaf to gently disinfect them

- Keep it under close watch in case the patches reappear.

Also, make sure it's not near other philodendrons, as to not contaminate them.

To prevent it from coming back, only water you philodendron from the bottom. If you mist the leaves, mist it with lemon water. Or even better, if you need to increase humidity, don't mist and instead, put your plant's pot on a plate of wet peebles.

Good luck fellow plant lovers !