Yo,
ppm = parts per million, the concentration of nutrients in your solution that you feed your plants.
pH is the acidity/alkaline level of the liquid you are feeding the plant with.
Usually you would use specialized testing meters to find these numbers out, there are good cheap ones on ebay. To me looks like ph problem too, the heat thing is not that big of a deal unless you start sweating standing in the same room as your plants.
Good luck, don't lose it now.