Is the fan shroud my issue?

okay i have a 78 model 350 and i put a 4core radiator in it the other day and drove it with straight water in it and it ran about 180-190 degrees but i added a fan shroud and a gallon of anti freeze and some stop leak because it has a small leak well now the truck is getting warm and im not sure if its from the pellets in the stop leak or the shroud. thanks