Thanks. I have potted it up and I shall see how it fairs.
I potted it up Thursday night, along with all the others. They have gone from 1L pots to 2.5L pots. They are all in the same mix of composted wood, composted green waste, rotted manure and perlite I have been using for a few months, a 5ML dose of Empathy Rootgrow Mycorrhzal Fungi was added to each root hole. I have also top dressed each pot with 10ML of Epsom Salt. I have tested the PH of the water and it is 6.5.
I potted up 10 plants in total and 9 of them are already showing roots at the bottom of the pot and plenty of strong growth, no signs of any problems. However, this same one is stunted and showing no signs of rooting at the bottom of the pot. So all I can deduce is that it is a runt.
TBH the Critical seeds I have are freebies. If you spend £25 with RQS you get a free "random feminised seed", they are always Critical. It's no big deal I always plant a couple more than I need anyway.
Also, I have invested in a VPN.
Thanks for the replies.