Don't use rocks or sand; just worry that the pot has NICE BIG DRAIN HOLES! That's what your plants want the most. And make sure the soil is very light. I'd add some extra perlite when you mix it up, to help it drain better.
If you don't have a pH meter, I hate to sound like a spokesperson for Canna and Botanicare, but the Canna Terra and Botanicare Pure Blend nute systems are buffered so that you don't have to adjust the pH as carefully. Be sure to flush out all that miracle grow chemmy fert though, because your plants look locked out already. I'd go with a plain non-fertilized potting soil, bagged compost, or promix cut with perlite by up to 30%.
stinkyattic Reviewed by stinkyattic on . ny grow journal, need slight assistance (pics inside) ok my plants are about a month old now maybe a little bit better, one pot that i have 2 of them in looks like they have some nitrogen deficiency. i say this because of the yellow leaves a bunch of them have fallen of as well, the other pot is doing pretty good but is now showing little signs of yellowing as you can see. i cant tell if this is too much water or nitrogen deficiency, it hasnt rained for like 3 or 4 days now and i havent watered to much to be sure any help or any Rating: 5