I have never seen that before.. i have had leaves turn purple but thats more black.. look at my avatar. 'THAT PURPLE' lol
what temperature is the room at plant level? temps have alot to do with colour change esp when in flower.
What is your setup?
What strains are you growing?
What medium are you using?
What is your PH of your water you feeding the plants with?
Are you growing in soil? have you checked the PH level of the soil also aswell as the PH for the water? - If your HYDRO disregard the soil ph.
What is your Nutrient Level in EC or PPM hanna?
What is your Humidity level?
How old are your plants?
What stage are your plants in, veg or flower?
What is your light cycle?
What times do you water, and the frequency & Duration?
How far is your lights from your plants?
What fan are you using 'if your using one' and if so is it 'oscilating'
When was the last time you flushed With plain water?
What nurtients do you use and how much?... do you have tools/ph/nutrient pens to measure this?.. if not guess work will only kill your plants some day or another.
Do you have a bug problem? Is your grow outdoor or indoor.
Do you have heat problems? fresh air problems?...
i can keep going.... get a checklist.. go through it and tick off everything if its ok until you find the one you messed up with and fix it before it gets worse.. im interested in finding out what these spots are.
i think these are all basic simple questions that should be answered and included before posting up a 'help me' post.. im sick of asking these questions.
These questions help us .. the 'VIEWER' to narrow down the problem for you so we know whats up and whats down.
I cant just take a look at a leaf and say 'thats your problem right there'.. we need explicit detail so we can give you the best possible answer we can.