hempy bucket ph rises within minutes very high, growing in straight perlite!

i am actually giving them around 3 ph water and checking the runoff 10 minutes later and its at 6.8 or so then give it few hours and its at 7.8. i am watering my plants every 4 hours or so to try to keep them alive with the deficiencies they already have from this fight. plaese help with this issue, i have done hempys in the past with great results. i have tryed out tap water, i got a RO filter. i even have two white widow seedlings about 3 weeks old in a brand new rinsed out bucket, they are showing signs of cal or mag def, because the ph raises instantly. i have flushed tell my hair falls out with water way under five just to get the ph to be in good range for a hour or so then it breaks out of range so it cant get its nutes. any suggesting , anyone have this prob? thanks brothers!!!!! see everyone at the gatherings!!!!

Since nobody has replied, I'll try an offer some quick suggestions you can try if you want.

pics ALWAYS help but

Try watering every 2 days instead of every 4 hours.
Try not using pH down or meters or RO water. Just tap water + feeds + additives.
....

Please let us know how you get on.

list all things you are feeding them with and the ec or ppm . Ph3- thats nuts
and I agree you may also be watering to often
double check your meter with ph7 and ph 4 testing solution.