Mn deficiency? Pics

Hi guys, I've taken some pictures (poor quality) of my plants today. The HPS made it look like I'm peeking through blinds in the one pic. :wtf: As you can see, the leaf that I removed has blackish brown tips and little spots on it. As it started yellowing, I removed it. There are quite a few leaves with these spots on them but they aren't yellow. Do you think it could be a Mn deficiency?

My setup is as follows:
400w HPS
lots of air
Hempy buckets with 100% perlite
GHE Flora Series nutes using Lucas formula (8ml/gal Micro - 16ml/gal Bloom)

strain: AK-47
been in flower for 2 weeks, just starting to bud
pH of runoff: 6.6

temps have been low here (cab is in garage) +/- 16C/59F

Otherwise, the plants are very bushy and healthy looking, they are still stretching a bit. Tops are very healthy. No bugs.

Any ideas? Is my pH a bit high for hydro? Temps too low? The weather should be warming up soon, we've had a ridiculous winter.

Thanks for your help. Cheers :)

Yes, 6.6 is too high for hydro. You want to stay between 5.8 and 6.2. If your using gen hydro stuff check out latewoods recipe in the hydro section. Gives you a all the ppm and ph info you will need during veg and flower.

Your temps are too low too. Should be around 75 lights on and 65 lights off.