Leaves turning Purple

Hello fellow gardeners,
Can anyone tell me why the leaves of the plants in my garden are turning purple.
I have had this problem for over 25 years.
Plants like , marigolds, parsley, mint, coriander , rose, all have a portion of their leaves
turning purple.
The plants that are grown in new pots with shop purchased compast, also have the
same problem.
Any ideas.

Thanking you kindly

 

Must be something in the air but don't quote me.

 

Earlier in the season I would have said that it was caused by cold weather - but that can't be so now - unless you are in Alaska.

 

Could you get some photos on here?

 

Thank you for your reply, i have added some photos of marigold , marjoram and coriander leaves that show the purple leaves.
Are these safe to eat ?

 

I've never seen it on the other plants you mention, but in my experience Coriander turns a nice shade of purple/red when it is about to set seed, especially if we've had lots of hot sunny weather.

 

It's edible... it's not looking like any pest or disease.. i would say it's a mineral deficiency of some type.. are you feeding them?

 

It's a physiological problem cause either by a deficiency, as Quercus suggests, or possibly overwatering. In other words, your plants are a bit unhappy!

This late in the season, I'd try a general purpose feed and be careful not to waterlog the plants.

 

Thanks for the advice.
The garden soil is clay type which gets water logged every time it rains.
But the plants in the plastic planters are in general purpose compost.
I will try using a plant feed regularly to see if it solves the problem
Thank you

 

Have you had your water tested? perhaps the PH is abnormal or it contains some other chemicals on minerals that ends up turning them purple? Do any plants that you never water (Ones that only recieve rain water) have any purple leaves?