Grand Daddy purple have a low yield?!!

I have 36 grand daddy purple under 4,000watts off hps. sum of them reached almost 4 feet tall. the buds look amazing crystals all over it and smells like a grape. but the only thing is that the colas are dont look that fat. there week 6 into flowering so they got 2 more weeks but from my expierence they look like they are going to pull a ounce and mayby 5 grams. Does this strain add weight the last two weeks or is it a low yield? shit I would be happy with 1and a half zips at least a plant but damn any less than that and It wont be worth it. I let my pounds go for 3500 no matter how dank it is so I kinda need a high yielder. anyone have a strain in mind that yields alot?

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awsome stuff man good to be u

lol dont post pic of u or a mate there xD

yeah but what about the yield. im hella stressed about the yield of grand daddy. those are just the ones that I take off the tables so i can fit the trays to water on. im aiming for 2 pounds and that would be less than a ounce a plant which is embarassing as hell.

Seems unusually light for gdp. Did they fill out at harvest? I would say go with one of the following, romulan, blue dream, northern lights x skunk. all are potent with heavy yields.

Well purple erkel is known to be a low to average yielder, you may have a phenotype leaning closer to that than the big bud.

Let it flower another week or two if they are still small at 8 weeks, just experiment.