If it were me, I'd mix the molasses and guano in with the water for one feeding/watering, then use MG BB at the next scheduled time. The reason is chemical components might impare each other if you mix them all together. Having said that, if you mix them into water and not just mix them together first, then add water, you might be just fine. At four weeks of flowering, how much longer are you going to grow them? Should be getting close to harvest and you should stop feeding and just give water the last week or two of flowering. It might be too late in the grow to add guano unless you want to flower for as long as possible. Go easy with it. Any chance you can put up some pictures?