So, last year I did a little trial.
I split my leeks into 4 batches - and by split I mean I got the tray they were growing in, and tore them into 4 quarters. I ended up with 15 in each batch, with an odd one or two left over.
15 watered in with seaweed feed
15 watered in with revive
15 with revive and used mycorrhizal fungi on the roots
15 with mycorrhizal fungi on the roots and watered in with water
They were all in a patch next to each other, with about 6 inches between each plant, in 3 rows of 5 for each batch.
The best all round results were the seaweed food. Second was the
mycorrhizal fungi on it's own. The two with Revive were both pretty much
My results are based purely on the number that have been harvested which means hitting about an inch diameter.
I wish now I'd tried the seaweed and fungi together. Next time maybe