Bleached looking spots on leaves. Heat issue or maybe chlorine ?

[Nugzinjugz]

Hello I'm a new grower. I have noticed these bleached spots on certain area of the room after I adjusted a fan. I was thinking heat could be causing the bleaching of the leaves but have herd of chlorine causing problems as well. The light is about 3ft from the one plant and a lot further away from a 2nd short plant both showing same signs . Using double ended 1k HPS . Environment stays between 69-79 F and 40-50ish humidity. Thanks KS for you input .

 

[NovaGrows]

Are you monitoring your PH? I've seen similar either the pots stay wet too long and PH drifts or just not monitoring when watered.