Bronze/yellow splotches on leaves?

I've got two plants in mid-flowering (honestly *blush* I'm not sure how many weeks it's been - I'm judging when to flush by the trichomes). Anyway, both plants are showing yellowish/bronzish patches between veins on their newer leaves and yellowing around the veins; it's more pronounced in one but can be seen in both Can anyone help me diagnose these babies? I've got a few theories (overwatering or maybe nute salt buildup) but I'm a n00b hobbyist and want to check w/ others before I jump to leaching the soil right away...

Looks to be more of a deficiency than a burn, MG possibly?! What nutes do you use? Other than that they look fine (from the pics I would say around 4th week of flowering maybe?)

Right now I'm using a mixture of Fox Farm Tiger Bloom (3 tsp./gal), an all-organic (and horrid-smelling, guess that's inevitable) hydrolyzed fish fertilizer (also 3 tsp./gal), and blackstrap molasses (1 tsp./gal). They're pretty well-balanced fertilizers (especially the Tiger Bloom), but I'll have to look into the specific ingredients and see if there's mag lacking anywhere. Thank you for the advice - they've been worrying me a bit; oh and if I had to guess the flowering time you're right on w/ it, props