Bug infestations are a sign of soft plant tissue. Not all plants will develop chlorosis but some tend to in a GH because of the extra heat and humidity. Plants grow faster and tend to not harden off as well as if they would outside in the elements. Thats why they are bug and mildew magnets. Its not strange growh its just more soft and suseptible to attack.
As far as cooling, absolutely shade cloth and fans. Thats all I use most of the time. My fan pulls in 1.5X the volume of the GH every minute. Its a big ass fan and its on a 30$ thermostat and keeps the temps right where I want them. But when its 100F outside, pulling in hot air doesnt help. Right now its 70F outside in december and I can keep my GH around 90F inside with just a fan. During summer I have to run 50% shade and a mist system. Theres no way to passively cool your GH if the outside air is hotter than what you want the inside to be. Its always going to be hotter inside a GH than out if the sun is shining. Now if you live somewhere with mild weather then you may be able to get by without any knd of evap or other cooling other than a fan. And in that case a GH would also be extending your season and providing extra heat you need. Where if you live in southern CA like me, a GH isnt helping a lot during most of the year. We already have a very long growing season, warm dry weather etc. It becomes a pain during summer to keep the temps below 100F. Thats why I am saying its better to just grow outside sometimes. Especially if you live somewhere that can easily pull off an outdoor grow and no need a GH. Keeping your neighbors from seeing what you are growing is not a great reason to get a GH. Trying to extend your growing season or raise your temps for better growth are good reasons. Im not knocking anyone for wanting a GH to keep whats inside out of sight, Im just saying it may be more trouble than you are expecting.
I have done tomatoes in the GH in winter. They do fine. I propogate avocado trees, cherimoya trees, mango trees, dragonfruit cactus, pineapples and a few others for commercial nursery stock. Avocados do the worst in the GH. Very prone to aphid attack and chlorosis. I have to feed the trees systemic pesticide to keep the aphids under control. My GH is absolutely golden this time of year though. Im propogating stuff that would otherwise not grow outside this time of year. And I will have them ready for sale in spring. And I could probably grow great weed in there this time of year too except for the photoperiod is too short. Would need supplemental lighting to veg the plants and keep them happy on cloudy days.
If you do some digging or talk to the big pot growers in Northern CA, they will tell you they only use the GH to keep the rain off their plants or to do light dep. They will tell you the plants are healthier and less prone to issues when they can leave the cover off the GH. Now I have no idea where anyone else is located in this thread. No one mentioned what state they are in. If you guys are in a more cool climate or one with more rain, humidity etc you may have totally different experience and or set of problems. I just want people to realize when you throw down a GH, its not just automatically a perfect growing environment. Its most likely going to need some adjusting and there will probably be unforseen issues. And it will probably cost more than you were origjnally expecting to get it all sorted out.