We have 3 different types of tomato plants. I have 4 that I started from seeds 1 I have no idea where it came from but it's doing well and the one Big Boy that my wife bought because she didn't think the ones I stared as seeds would grow. Now I treat them all the same even though the ones I stared from seeds are better

But I'm having a problem with the Big Boys cracking a lot at the top. All the other ones are having no problems cracking. Am I just watering the big boys to much? I haven't fertalized them except for egg shells and compost. Thoughts?