yea i had mildew when i was growing the "heirloom" seedstock. part of why i switched to well bred cultivars. Altho, only my determinate bush plants were getting mildew... so air circulation is probably a bigger factor here.
what are you spraying that is defoliating your plants tho?
For my paste tomatos i like the san marzano plant. its a straight up super vigorous indi, i prune it to one stem. it produces pretty damn well that way, but will BER like nobodies business... this atrium gets rained out a few times a year by the big rain storms we get in houston. when that happens the fertilizer charge is washed out, and the marzanos get BER like... 2 days later, very finicky plants, but worth it imo, if you want paste atleast. THE BER is not terminal tho, it will just scab over as the fertilizer charge builds back up.
this, washing out is part of why i like rockwool bags... but at like 10 bucks a slab ( 8 bucks a slab + 3 4" cubes) ? eh you cant do too many without feeling foolish.