Q.tomato plants
I’m growing Beefsteak tomatoes. They are about 12″ tall and have all their leaves at the top like a umbrella, flat and round. One had lots of buds on but pinched them off. Could the cause of this be stunted growth or are these type of tomatoes like this? First time growing this type. Grew other types and they grew really tall and did good.

Loss of leaves could be due to pest, disease, watering issues, or nutrition problems.
Are the leaves, yellowing, curling, turning brown, spotted or distorted?
The links below will help you pinpoint the reasons.
https://www.gardeningknowhow.com/edible/vegetables/tomato/tomato-plant-problems.htm
https://www.gardeningknowhow.com/edible/vegetables/tomato/yellow-tomato-leaves.htm