In my opinion, grow bags don’t really offer enough room for the roots on their own. So to get round this I tend to use 10ltr paint buckets, with the bottoms cut out then twisted into the grow bags , then the plastic that was cut is then taped to the side of the tubs, this in my opinion has allowed me to control the watering far better. I insert cut sink waste pipe into each tub then this gets put down into the bottom of the tub, which allows me to water the roots, but I feed the toms on the top once a week, after the 1st truss has formed using s-chelate 12star, as yet in my short time of growing toms (15yrs) I have only once had blossom end rot, and that was only on one plant .
I know when I talk to some growers they think I’m bonkers to do it this way, but I have found it works for me. At the end of the day we all tweak things when gardening.