low temps high ppm and high temp low ppm.plants dont like lots of nutes when growing in high temperture.Some one told me this before it may even have been you stinky attic and it worked for me if you are hydro you dont want the res temp rising to those measurments you will get all sorts of problems i had the same kinda thing oing on in hydro and once i added antoher outlet fan and lowered the nutes all went well.be safe the postman.