The leaves unfurl in a deformed manner, it will unfurl in a unusual shape, or be crinkled or translucent in some parts. I can't see any bugs, however it typically only happens on new leaves. I apply a fertilizer however it doesn't seem to do much.
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2Can you add another photo showing the whole plant and preferably its pot please – Bamboo Dec 11 '19 at 12:23
2 Answers
More finicky Philodendrons have unfurling issues due to low humidity but with your plant it should not be an issue.
I think what you have is a pest issue, probably Thrips (but can be other as well). Here are a couple of images from a Monstera and a Philodendron Brasil that had/has Thrips infection and look similar. These insects are very tiny and very hard to spot. There is a chance that those white speckles on the leaf of your plants are them.
With these plants the latest leaves unfurled for weeks and got damaged and deformed.
This Monstera leaf was stuck for weeks, when finally unfurled the problem revealed itself. The right half of the leaf what was the inner half and got stuck. That one got most of the damage as it was hidden from the treatments.
This Philodendron Brasil due to its thicker leaves suffered deformation mainly and generally looks better than the Monstera. Now it seems to be clean of Thrips with a smaller than before, deformed leaf.
I usually treat Thrips with a mix of diluted Neem oil, dish soap and water multiple times over several weeks.

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tip burn! it looks like fertilizer burn but it may not be your fault!
the cold weather could affect nutrition uptake as well as evaporation from the leaves the leaves could be drying out from low humidity or excessive evaporation from a fan/radiator
check your ph tap water is around 8 depending on chlorine content.
this plant requires very little nutrition so any decent potting soil will be fine. also it is liable to change from variegated to plain leaves if given strong direct sun light.

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