Need Help , my PH keeps dropping

Hello
I've been strugling with my indoor plants for a few yrs now .The soil PH keeps dropping , Is this normal ? I've tried a few different soils and mixes such as B-Cuz mix , Biocanna or just potting soil with perlite added for drainage .I sometimes mix Lime into the soil . I use RO water with a ph below 6 that I adjust using either Nutrafin PH up or Proguard Potassium Silicate. I can put water in at a ph of 7 and the runoff is still way below 6 . If I flush with ph adjusted water the ph is good for a while but it still drops in a couple of weeks . The plants keep getting dark reddish stems and browning leaves , I believe thats lockout .

I use a 400w hps
oscelating fan
79degrees at daytime
68 degrees at nighttime
Nutrients - A recipe for success
water every 2 or 3 days
PS I have noticed that if I leave a container of PH adjusted water for a couple of days , The PH will drop from 7 to 6 . Is that normal . Should I just be flushing more often or is there a better ph adjuster I should be using
Thanks all

A few suggestions. Are you up-potting on a schedule? Up potting is important. The pH buffering capacity of soil will depleted over time, volume dependent. Up potting replenished the nutrients and buffer capacity for the next stage of growth. You should be starting in 8 - 16 oz containers, after 2 weeks up-pot to 1 gallon for the duration of veg and then up-pot again just before or just after flipping to flower to either 3 or 5 gallon pots. 3 gallons is usually sufficient for the average hobby grower. Consider buying a fortified soil. You can reduce your nute input by 75% reducing the likelihood of salt build up and you start with a soil that is properly buffered. This will help with pH over the longer term. I highly recommend FoxFarm Ocean Forest. I veg for 6 - 8 weeks. They get only 2.5 ml of grow formula 2x during the last 2 weeks of veg. In flower they get 4 weeks of increasing strength bloom formula starting at 5ml / gallon and topping out at 10ml / gallon weeks 3 - 6. Not much at all. This is because the soil is fortified with a range of nutrients. I used to face periodic pH issues. I have been golden since I switched. Note nute strength is strain dependent so you will need to figure this out as you go. Are you watering when you think they need water or when they are actually ready for water? They benefit from getting pretty dried out. Next time you water lift the pot. Note it's weight. Lift the pot before you water to gauge the weight when it's dry. Over time you will gain a feel for when it needs water based on the weight of the pot. I water 1x every 3 - 5 days depending on their stage of growth. More in flower, less in veg. Again, this is strain and environment dependent. Try to stretch your water schedule a bit. If you are using RO water then be sure to add some unsulfered molasses to your mix, especially in flower but take care as it acts like a multiplier for other nutes. Keep reading and good luck!

Hey Bigsby
I am uping the container size a few times depending on roots . I don't let them get root bound but the roots aren't growing like they should due to the ph. I water when containers are light . I have been cutting the nutrients down at least 50% from recommended . I am not getting salt buildup with the RO water I have not heard of unsulfered mollasses but I'll check into it.
Thanks

Molasses only really needed in flower. Helps with Magnesium and Calcium which is stripped out by RO process.

I would change the soil to FFOF. It will take care of your pH issues.

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Thanks Bigsby
The nutrient system I am using (Recipe for success)should have everything I need in it .and I might have a hard time finding FFOF in Canada . What about switching to something like a straight Perlite-Vermiculite mix . Will that work ?

If you occasionally mix lime into the soil and you are having lower ph run off than start, you might want to consider gettin rid of the lime. As any kind of lime has extreme acidic levels. If you go with a soiless mix try pete moss it has the strength to keep your roots grounded.

With soil-less mixes you must keep VERY close tabs on pH. Also, it is more akin to hydro so you don't run the same pH as soil. 5.8 vs. 6.8 but do your homework as I have never done hydro. You can get FFOF in CA or the equivalent. Roots Organics is good too. Trust me. Go with a well fortified well buffered soil. It make it SO easy. Then you can dial in with advanced nutes and other gimmicks if you like. I don't mean to be rude. Just speaking from my own experience.

I also had your PH problem a while back when I wasn't able to get my usual good soil. I had to use a cheaper soil mix and it showed pretty quickly in the plants even with up-potting. The buffer lasted just a couple of weeks and even repotting wasn't enough to help the plants. I added lime but the damage was done and the girls didn't perform up to their potential. Once back with my preferred soil and all was well again.
If you PH is off then nothing goes well, and even with lightening their feeding the plants aren't able to properly utilise what they're being given and problems can compound. Its a frustrating thing I know, and I second bigsby, that if you stick with soil growing then try to find a Canadian version of what the Americans use. Without a good grow medium its a constant battle thats gets pretty disheartening. Good luck :)

Thanks for the replies
I have used good fortified mixes such as BCuz which was recomended but I am told that due to the high peat content it can go acidic . I usually transplant about every 4 weeks but that varies abit . I use Dolomitic Lime to keep the ph up but it only seems to work for a couple of weeks . Maybe I need more lime but I would rather treat the disease than the symtom.