Help please! pH or herbicide damage?

Hi all, looking for some help with some tomatoes I transplanted in the middle of October. I am in NSW, Aus and people in my area are having lots of success with their tomatoes setting flowers and fruit.

They were in their nursery containers for a couple of weeks before planting and were growing really well and all were ready to flower when moved to soil.

I recently filled the beds with veggie/ seedling mix from a popular landscape supply before planting the tomatoes and they had some impressive growth for a week or two but have now stalled after a short period.

Only one tomato to show between six plants and lots of tiny flower buds that turn yellow and dry before opening and curly leaves/ new growth.

I have tested the pH and it’s come up as very alkaline, just unsure whether it would cause this degree of stunting and curling?

Thanks in advance!