La Diva Autoflowering Grow

1. Are you growing from seed or clones? Seed
2. How old are your plants? 4 weeks
3. How tall are your plants? 15cm
4. What type of hydro system are you using? wilma system
5. What brand/type of nutrients are you using? Canna Aqua A+B veg + flower
6. What is the Ph of your nutrient solution? 5.9
9. What is the temperature of your nutrient solution? slightly above room temp
11. Does your pH show a rise or fall when you do your daily check? Not really maybe 0.1 or 0.2 either way but ot daily as is quite stable
12. Do you foliar feed or spray your plants with anything? jus ph balanced water
13. What kind of lights do you use and how many watts combined? (HPS, MH, fluorescent, halogen, incandescent "plant lights") T5 mix ble/red 33,200 lumens
14. How close are your lights to the plants? 5inches
15. What size is your grow space in square feet? 1.2 x 0.60 x 1.8
16. What is the temperature and humidity in your grow space? 28degrees humidity 45%
17. Have you noticed any insect activity in your grow space? No insect or pest activity noted!!
18. How much experience do you have growing? second auto grow
This has spread over the plant, I'm concerned and confused as to what could be? It hasn't affected growth or other plants, any ideas on a cause and how to treat this? have tried flushing her with ph'd water but no change. HELP!!!