Question about filament life

[ThreeDeeMan]

Hi All, I am a newbie with a recently purchased Ender 3 Pro.
I added a glass bed and Capricorn tubing after purchase.
For several weeks it has worked just fine. I use only PLA.
Some days ago it started to fail early on in printing - just a mess of filament on the plate.
So I read the forums and did the following:
Replaced the hot end head (assumed blocked) and associated bowden tube
Double/triple checked the bed is level.
Used only default settings for several different prints.
Attached image is a failure example. Filament everywhere!!
Now, my question please:
Could this be due to filament being left exposed?
I have three reels of filament and they are not stored in a sealed dry container - just the original unsealed plastic bag with the original tiny silica gel sachet.
Purchased in July so stored for about 8/10 weeks. One reel left on the printer when not in use.
I have tried using two different filaments with the same results.
Is there any way to test/check if a filament reel has 'gone off'?
If it's too brittle, should it snap off by hand.
I am hoping the problems are due to bad filament. How might I know?
Any other comments appreciated.
3DM