about the "cold water" - it reduces the water matrix potential and then roots have a harder time drinking. (but only temporarily as the pot will warm again.) so it may cause some short-termed drought stress which has been proven to increase cannabinoid content. however, this is certainly not set-in-stone as this stress calls for a response that can also be initiated by UV/photodamage (among others) do, so depending on the situation drought may not do a thing