The reason behind this is plants produce trichomes during dark periods, they act as natural sun screen for the plant. Cannabis can survive for around 72 hours +/- on stored energy. So in theory leaving them in the dark for 72 hours will force them to produce more trichomes and increase potency.
Looking good. Just chopped one of my WW's yesterday.
I started flushing a week and a half before cutting (I'm also doing DWC) They probably would have been fine with 4 or 5 days though.
Google...
http://www.google.com/search?sourceid=chrome&ie=UTF-8&q=tincture+bottles#q=tincture+bottles&hl=en&safe=off&prmd=ivns&source=univ&tbs=shop:1&tbo=u&ei=vGobTaSUK4H58Aa824yVDg&sa=X&oi=product_result_group&ct=title&resnum=3&ved=0CD4QrQQwAg&biw=1336&bih=807&fp=a20cfd04ba3c5cf9
Hope that helps.
Your LED panel looks an awful lot like some I bought off ebay. They seem to be crap imo. I just noticed this morning one of them only has a few blue lights that still light up. I've only been using them for side lighting so I really can't say if they work. However I won't be buying more of them.