Any tinting of the water will skew the ph test results. Usually not even in the ballpark if the water is colored at all.

Not at all sure which members are in coco, but the grow logs might be a good place to start. You might also want to check in the outdoor growing section to see what it takes to ammend native soil(s) for indoor use. Usually a bad idea due to the bugs and microbial stuff though. :thumbsup:

Yes, the low ph will start locking out nutrients causing the yellowing, and 'the claw' effect on leaves. Plants will start greening-up once you get the ph within range.

Egg shells, dead fish and coffe grounds have been used for many years outside in the garden. But with some of the ingredients, they need to be broken-down into a usable form before it can do your plants and their microbes any good. Especially the calcium. You may not have mentioned it, but it's info all members can use.