Don't you have any photo editing software?..Most of them have easy tools for sizing/compessing pics. I use MS office picture editor. Soooo easy even I don't have problems. But there are hundreds of programs out there.
Lotsa' freeware on the net too.
I think you may have struck on the problem. My guesse is either salts buildup, which is locking up your nutes, or possibly extreemly rootbound, or both. Your watering schedule could use some adjustments too, IMO. I feel it's better to saturate the entire medium well, then don't water again for several/few days. Untill the medium becomes dry at least 3 inches deep, then totally saturate again. MJ prefers drought to wet feet.
My suggestion for the next trip into flower, I'd repot into fresh soil/bigger pots, shortly before putting them into 12's. I have repotted during flower, but don't consider it wise, any shock at this point really reduces final yeild.
That, or at very least, a thourough flushing (3-5 times the amount of water as the container size. i.e.-4 gallon pots=12-15 gallon of water) That should cleanup any buildup in the medium AND wash the roots. Let it dry really well, then resume a feeding schedule.
I'm sure grimm will have an idea r two, too.