Looks like something is going on at the roots - something munching away. I'd remove from the pot, remove all excess soil from the roots. Give it a soak in hydrogen peroxide solution for about 30 minutes or so. This will eradicate, mold, bacteria, bugs, and all pathogens. Re-pot in new sterile potting mix.

is it all of them or just some. If it is all of them then I suspect they all need a good feed.

Hi Seaburngirl

also thank you Bathgate

It started last week with one then two now this you can see in the photo , they have had slow release fertiliser and I do have a seaweed feed going spare if you think that may help

as you can see from the other pots are fine all in the same compost but they are all different varieties