This is my first time growing tomatoes and some of them are growing with brown, rough patches that look like this. Any idea what could have caused them and what the remedy is? They are planted in the ground, fertilized with a 6-2-2 tomato fertilizer, watered regularly with a watering can (though there has been heavy rain recently), and sprayed with an End-Rot solution and insecticidal soap. Thanks in advance.
Someone with more in-depth analysis may have a better suggestion, but I note in your second picture that there is a fresh crack on the left-hand side, and my gut reaction is that this is cracks scabbing over.
Cracks can come from uneven watering (such as heavy rain), as the fruit swells when water becomes available and bursts the skin.
Given the level of fuss I'm not prone to put into growing the things, my personal response has been to shift production entirely to small or cherry tomatoes, as this seems to be a much worse problem (in my garden, anyway) for large tomatoes, and when a cherry tomato does crack badly it's a lot less waste if it's got to the point I can't salvage it.
...but I could be wrong.
(it's also possible that something is nibbling on your green tomatoes and they are scabbing over, but that looks more like a crack to me.)
Hmm - this one just percolated up in my brain, though it's supposed to be more of a blossom end condition - "Catface" (Minnesota Extension). UC Davis does mention the water issue as a contributing cause. I guess Minnesota just calls that growth cracks (just above catface on their link.)