Low ph problem

I’m in week 6 of flowering in soil and realised my leaves were turning yellow, so I tested the run off Ph and it was at 5.5

I’ve flushed the soil in 30litre pots with 60 litres of tap water at ph 8 and the soil ph only increased by 0.2 im really struggling to increase the soil ph and coming near to the end of flower I can see my plants aren’t getting enough nitrogen due to low ph and is effecting the overall growth of my girls.
I’ve also put in limestone but doesn’t seem to be doing the job it’s as if my soil ph is stuck at 5.8 even tried 20 litres of ph 10 water and run off still came out 5.8 need help urgent
Thank you

How many more gallons of water before you realize this is futile and that you’ve waterlogged the root zone? Of course limestone didn’t work. Its not rapid deployment. Post some pictures in normal light for better advice.

Stop flushing it. Let it dry out, then start watering normally. You'll see all sorts of deficiencies develop when you flush like that. PH might not even be your problem, you might simply be not adding enough nitrogen. What nutrients are you feeding and what is your schedule?

I’m feeding them Genesis 3 part with Buddhas tree pk booster 5 litres every 2 days

Stop with the flushing. Espoma Garden Lime will bring your PH up ASAP. ~5ml per 4 liter of soil mixed into the top layer and you're PH should shoot back up to ~6. That said, I wouldn't be freaking about 5.5 too much.