This late in flowering extra P isn't needed but you are adding so little with the Mammoth P that it won't hurt and the other goodies in will most likely help.
I'm not sure what urb is. I grow as simply as I can using all AN nutes with ProMix HP for my 'soil'. Don't need no damn microbes messing with my grows!
At this stage you could us some Epsom Salts to boost Mg and S. Sulfur is the 'secret' ingredient in good bud boosters. I use AN Big Bud for that. It's 0-15-35 with 10%S. 20 amino acids, citric and ascorbic, (Vitamin C), acids. I hate to grow without that and have tried a few others over the decades and nothing seems to work as well.
Bashers can bash but even the basic 3-part nutes from AN come with aminos, fulvic and humic acids and many other things that GH for one does not include in their base nutes. When I bought the gallon jugs of AN 3-part I have now GH was almost $10 more per jug and the AN wasn't on sale. Plus with the pH Perfect technology I have never bothered checking pH whether I'm growing in soilless or DWC but I only use RO or distilled water for both. Try doing a whole grow from clone to harvest with GH in DWC without ever changing nutes and see what happens. A buddy using GH and my DWC system failed miserably. He was trying to teach me how to grow and had never actually grown pot but had hung out with a grower who convinced him that GH was the 'bomb'. Blew up in both their faces.
The only other things I use from AN are Rhino Skin for silica and I feed low levels of that from seedling on up. Big Bud of course and I got a free 500ml jug of Bud Factor X that shows promise but haven't used it side by side without yet so still not ready to pay for it. Any old CalMag will do and Epsom Salts just to cover the Mg and S. Most of the others don't interest me and are very over -priced which gets the haters all hot and bothered. Name me a nute company that doesn't hype their products but at least AN is made here in Canada and the US using quality base products to make theirs. GH sources most of their salts from the lowest bidders mostly from China and are owned now by Scotts/Monsanto along with Botanicare and Gavita so I'll never use any of those.
One thing I do that isn't in any grow manual is add extra supplements like zinc, iron, selenium, B-Complex and chromium with vanadium from pills/caps I use for my own health. I grind them to powder in my mortar and pestle and add them to a plain water feed between nute feeds. The zinc IMO is especially helpful and plants use it as a catalyst for many of the chemical reactions that they need to do to make many of the things that help them grow. I feed that mix two or three times per grow in DWC too.
As an older dude I use zinc to prevent those thrice nightly trips to the bathroom too.
Zinc citrate is best and if it has added copper even better.
Today I bought a bag each of sheep and steer manure to grow some 'organic' CBD pot for a friend that is fussy about these things. Gonna need some sort of 'zyme product to help it work and have worm castings to add to the mix as well. I'll use my ProMix for the base as it's organic too. Did that back in '78 when I grew my first buds and it wasn't so great but I know a lot more now and that should help.
I currently am growing Blueberry OG by Barney’s farm. My bud looks more sativa. If anyone has a comparison grow that would be helpful!! 
