question concerning coco coir and pH "down"

my plants are all between 25-30 cm tall, and they've been going for about a month now....they're doing alright, but i've a couple of the widows are a little too lime green, as a result of not being on the ball with nutes, which i'm now on top of. i'm growing in roots organics coco coir, and i need to know how to lower the pH of my water (which is distilled) before watering the plants..my pH isn't too bad right now, but i've always heard that keeping the pH down can be a pain in the ass in coco, and i feel like a few of my girls should bigger than they are. it's amazing how much vague information there is on the internet about this...i saw that there's a product called "ph up" and "ph down", but i've also read that they're only short-term answers and they eventually build up in the soil themselves. anyway, any info anyone has would be greatly appreciated.

 

Ph down is an acid which over time wears off and the ph will move upwards again. Ph up is a carbonate which is lime chalk or shells.
Peat's a natural ph downer so maybe adding that to your mix will buff against a rising ph. even natural citrus acid will move ph downward.

 

buy good coco mix and buffer it to ph 5.5-5.9.
the coco is quite stable and holds its ph level quite well if your feeding is correct.
Buy Ph down, its phophoric acid.....use it to lower the Ph of your nutes to 5.5-5.9 before watering.
Keep the Ph level of feed at a constant throughout for beginner.