20 cm away with a 150 Watt HPS is too far away. I would aim for 8 - 15cm.
With 8 cm away the top of the plant will be getting about 25,000 foot candles and 15 cm away it will be getting about 7,000 foot candles. 20 cm away and you're getting less than 5,000 foot candles. So really the closer the better.
If you find the top of the plant is going yellow back off the light. If you can put your hand under the light with the back of your hand facing the bulb and hold it there for a minute comfortably without your hand getting 'hot' then the plant will feel the same, then it's good.
Hope that helps.
Also dude I can't see your photos. Lots of people are still having issues viewing photos on the site. If you upload them to IMGUR and paste the link into your post it's better that way. Thanks.