couple ?'s

hey folks. currently growing ak47 / lowryder 2, sprouted them on Dec 3rd in soil and things arnt exactly going to plan.They were started under 250w hps and from the 3rd week in they went under 400w hps.
Well one of my 2 plants is much smaller than the other with her being in a smaller pot and she isnt looking bad, buds have formed nicley and not too far from finishing. But with my bigger plant which is in a bucket is struggling to finish budding, lots of buds and the colas was looking decent until she suddenly took a major hault in growing a few weeks back. She has been flushed but no sign of a rapid recovery and she is plodding along slowly.
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My questions are 1 about a metal halide 250w bulb, if i get one of these for my next grow (which will deffo not be autos) for vegging will that keep my leaves in better health for longer? because with the hps i just seem to be killing them way too fast and the plants are struggling to finish with lack of foilage.
Another is about soil, i just used multi purpose bought from a local garden centre along with perlite and not sure if this soil is doing the job for my weeds?
One of my grows was done with john innes soil which seemed to be decent enough and i wasnt getting the troubles im getting now.
Sorry about the essay but if someone can chuck us some pointers il be grateful and + repping!!

I grow autos perpetually......start all under T5HO in a solocup for about a month...using Humboldt Soil (nuteless)...slowly adding appropriate organic nutes (biobizz) ..transplant to 4" pots, then on to 550w HPS. Problems typically involve overwatering and overnuting.....most of that can me overcome by growing patience first!

thanks for the reply oldreefer + rep.
This will be my last auto run, i went for them to have this done within 10 weeks but that is not going to happen now looking at my big plant.
i was given a free seed from the tude when i ordered a kannabia white domina fem so im just gonna be doing that 1 after this.

Will an MH bulb not help me at all? i'd rather not have to be ordering new lights as i have soil, ph kits and other things to be getting.
I am using bio bizz grow and bloom, but i think i may have went too heavy with the bloom on these autos and the big 1 must still be locked because all thats happening is leaves ae dying and shes budding awfully slowly.
I shall search for some humboldt soil now.