I grow in a greenhouse too. I've found keeping the tomato plants moderate size, one per pot (I use 100L pots), well trimmed, with good ventilation helps. Plus I spray generously usually with Mavrik otherwise everything in the greenhouse gets eaten by bugs. Tomatoes can get so many diseases I usually don't bother. Copper makes a mess in a greenhouse. I cut the laterals off when I see them, but sometimes they get away and grow tomatoes before I see them if I'm away for a week.