Overwatered or Underwatered???

I'm having a hard time with my watering cycle. My moisture meter says the medium is dry but it doesn't feel dry and the bucket is still pretty heavy. It's been 5 days since my last watering and I'm in the first week of pre flowering. Leaves are starting to turn yellow and turn upward. My Ph is between 6.5 and 7. I'm using Promix in 5 gallon buckets with Flora Nova Bloom as well as Hydroplex and a touch of Superthrive. No bugs adequate ventilation with a 600 HPS bulb. None of the books or sites show very good pics of deficencies so I'm scratching my head.

In my experience,

It sound more like overwatering than underwatering to me.

But it could be neither.

I have never used a moisture meter as watering soil should become an instinct. You should be able to just look at your girls and know whan they need a drink. 5 gallons of soil is a good bit and will retain water for quite a while as long as the girls aren't extremely huge.

I always let the girls start to droop a little. So they can breath. Then they get a good drench and repeat.

You say ventilation is good so is it safe to assume your temps are ok?

You should be able to find a good thread on here about common plant problems, there is a sticky.. You might be experiencing a little nute burn using the nutrients this early into flowering. Depends on your medium. I would suggest checking the ppm/ph of your water and then the run off.

Wha are the temps like in your grow area>? what is you realitive humidity? If yo have low humidity there is no way your soil should be wet after 5 days.

Most plants absorb water at a constant rate and should be watered on a schedule. It is also reccomended that you alternate your waterings, Water with Nutrient enriched water and the next watering with Fresh water. You should be checking the ppm when you do the freshwater to see if your girls uptaking as much nutrient as your putting in.

The temp is 78 during the day and 65 at night. The humidity is steady between 55-65%. The medium I am using has no nutes in it (Promix).

explain how you are mixing your nutes

and STOP using superthrive it Is NOT a nute or food and can kill your plants very easily

Pics would help make advice closer to right