I had the same problem. Had zero tomatoes for a while. They're coming on now though. Where are you, I'm wondering if it's the MC from one location. I've used mushroom compost before and never had this happen. I dug up the clay in an area that had been a lawn.

My plants are tall with stems 3/4" to maybe 1 " thick. Never saw them so thick.

I have 25 tomato plants plus a couple volunteers from heirlooms there last year.

Googling found this article which if I paraphrase what they said is: If you apply too much nitrogen the plants won't produce tomatoes till the excess nitrogen leaches out of the soil.

I've had this happen before in very good garden soil. The plants grew 12 foot tall but produced a normal amount of tomatoes for a normal sized plant. Also don't remember that they were at all late. My yellow pear plant did produce a lot of tomatoes. The beefsteak production was normal.

I've converted my clay lawn to gardening before. I had used peat and sand with some mushroom manure. This time I decided to use only manure for one reason because peat is $90 a cubic yard. So what I did was make the soil look nice by mixing in the MC. I dug in about two inches and then spread some more on top and chopped that in with my spade till the clay clods were broken up.

I started this last fall using horse manure in my potato bed. I switched to the MC because my fatigue problem limited me to only getting one cu yard on a one day truck rental.

For next years potato/tomatoes my plans are to dig in two inches of horse manure in my lawn, and then pile my leaf cleanups on that area over the winter and dig them in next spring.