We are having the same problem with the lower parts of tomates leaves being yellow...I believe that it from too much rain...then too hot ...then too much rain again here in Pa until Next Monday so I just trimmed it off with clean scizzors................for the pumpkins............if you can leave 1 pumpkins on the same vine and cut off the rest of that vine....go to the next vine do the same thing...that way all the energy is going to 1 pumpkin per vine don't touch them with bare hands when they are wet.