My doctors’ nurse has bouts of diverticulitis and she gave me great advice. When you feel an attack coming on cut out all roughage.
Stick to fluids, no dairy except a good probiotic yogurt. Be gentle on your tummy until the symptoms subside. Drink lots of water is the key and never allow yourself to get constipated. Mirolax if you do. I was eating all kinds of healthy roughage and taking Metamucil when I was having an attack. It made it worse. Once I started the kindness to my tummy routine I improved rapidly. Hope that helps.