70-80% humidity is way too high for flowering, it will more than likely cause mould.
Around 40-45% is much more reasonable for flowering, even lower would be ok.
Cannabis, even in veg, does not need high humidity, it is not a rain forest plant.
Warm days, cool nights, dryish soil and low humidity are optimum for peak trichome production.
30 degrees is not overly high and your plants will cope with those temps just fine, however they will drink a bit more than usual.
Hope this helps,...........
Organoman.