Ya man I can definetly help ya out. get some fugicide spray or power for the powdery mildew. for yellowing pic up some calmag and grow big, works great and you wont have lockouts in veg feed these to them every other watering your will have nice green follage. In flowering use tigerboom with the calmag it will keep your plants green in budding and the buds will be nice, dense and greasy. For humidity control in veg leave your door of your grow room open 25% the humidity will go down quite a bit and in flowering open your door for 15 minutes before the light goes off the heat will excape and lower your rh which will result in trichlome buildup also know as resin glands.
check out my grow I have going rightnow that is big bloom and calmag in veg.
for flowering I am using tigerbloom and calmag (works awesome) no lock outs follaige is nice green
. I am in 37days flowering still got another 30 days to go.