Hello there,
I need a little help. My girls started their 4th week flowering, they look allright to me except some lower leaves what started to turn yellow and fall off. When I see them in the grow light (400W HPS for flowering), the leaves on the top are brighter, than the other leaves (they look darker). Today I've check them in various light conditions (with HPS they look brighter, with my phone's photoflash light they look a little bit white green, with my camcorder's photoflash light they look a little bit yellow and with a normal bulb they look nothing special). The problem is that I really cannot decide that there is nitrogen deficiency or not

The top leaves are new ones, the are growing bigger and bigger day by day but this color variance makes me a bit nervous. I don't want to overfeed them, I try to do everything allright.
Some additional information: Amnesia Haze strain. I grow them in soil, smart pots (12 liters / 3 gallons) I used to check water PH, I use Plagron Alga Bloom (NPK: 3-2-5) I used to add 40 ml Alga Bloom to 10 liters of water. I water them every second day with 0,4 gallon (1,5 liters) of Alga Bloomed water / plant.
Are they okay and I'm too nervous or should I change something? Thanks for the help!