Hey guys, i suppose the title says it all - i've got 2 plants that during their veggie stage were growing nice and big, plenty of branches and large leaf to go with them. Now they're in their flowering stage there is only about 3 weeks to go until harvest and bud development seems pretty minimal and stunted. Flowers are in all the right places, but are not very developed. Any ideas what can cause this, or anything i can do to boost bud growth?
Many things can cause stunting. At this point forget 2 or 3 weeks till harvest, they will need more time. How much time depends on whether there are more setbacks but from what you say I'd say add a couple weeks at least. Harvest times are just an estimate and seed companies base them on optimal conditions. Botom line is, they are ready when they are ready.
My point is - as far as these plants go you should look at them as if you're seeing them for the first time. Forget how old they are and what their past has been and just take them where they are and try to move them forward. This is a good reason why a detailed grow journal is a good idea. It might be possible with that to track back and figure out what went wrong and when but now it would just be a guess from what you have said.
They are on 600w hps light for 20 hours a day. The only nutes they have had was rhizotonic during veggie growth, and 5ml of big bud per litre of water about 4 times per week, plain water the rest of the time.
OK, autoflowers seldom harvest as early as they say and they don't produce huge buds or yields. Get it on 12/12 light that is a blend of 6500k and 2700k. Maybe add about a 65w cfl sidelight. I'm not familiar with those nutes so don't know about that. And are you checking pH and temps and humidity?
I'm not too sure that autoflowering plants need to go onto 12/12. I always thought they were designed to grow by duration of growth, not light frequency. So they would flower automatically at say 5 weeks, whether i put the light on 12/12 or 24/0.