First and most important...what are you using to test your ingoing ph, and the runoff ph?
You mention you're in a medium intended for roses? Roses are acid-loving so I sincerely doubt it's ph is buffered that high.

Does it have any perlite in it? A couple of the pots look like you stuck a plant in a cow-pie.

You adjust all your ingoing water to 5.0ph? Geez...that's gotta be 1/4 cup of cider per gallon of water, isn't it? This is likely the reason they're yellowing. Adjust your ingoing water ph to 6.8ph, and give 'em a couple of days to see if that helped.

I'm almost afraid to ask...but what did you "solve"?

Putting anything that has not been composted into your pots, is a great way to promote rotting soil. (coffee grounds, citrus peels...) Shit like that will rot. You've heard of beneficial bacteria...? Well conversely there are damaging bacteria, too. And egg shells are not a good source of calcium. (it's not in a form the plants can uptake)
All that stuff is great in the compost pile, but bad in pots.

Likely a good idea to learn to grow before you try experimenting with your own soil mixes. I've never used coco, so have no comment other than it runs at a lower ph, and is notorious for salt (nutrients) build-up. Peat based mediums are somewhat cheap, fairly forgiving and easy to find. If you have the experience to dial-in a working soil...then have at it. But you're setting yourself up for failure if you don't know what you're doing.