you dont want no old roots att all mate, you want to siv out any big uns, then rinse with the cannaz, leave to dry out do again if needed then just give it a rinse with like quarter strenght a&b an your good to go, an if you flushed the coco with plain water before you cropped you probs fucked up your buffers so ph will be fucked, an you probs killed all your micro life you built up.
heres a little guide for canna coco mate stick with this an you cant go wrong!!
Canna Notes:
Rhizotonic: - Develops roots and can be used as foliar spray after transplanting or to reduce stress. Use the Rhizotonic at the high end of the spectrum (10ml-15ml per gallon) during the early stages of veg. Once the root system is big and established and you are in your final size container, then you can drop the dose down a bit, and once you are a week or 2 into 12/12, then u can drop it down to 2ml per gallon until about week 5 or six. For foliar feeding (until flowering starts), mix the Rhizotonic at 2ml per gallon. Spray it right when the lights come on, while the room and plant temps are still low, and so the leaves have time to dry before dark. Use it 3x per week, or every other day.
Cannaboost: - Kind of useless, but good as foliar spray. Use it at the low rate, 8 ml/gal applied every other day. It has little EC and will not affect the plant to much. Also, only adjust the pH if it is way out of bounds but if between 5.2 and 7.9 don't worry about it. Apply from the point of photoperiod change (12/12) to about 1 week prior to harvest if possible.
Cannazym: - Stimulates bio life - rinse coco with double dose cannazym after harvesting to use the coco up to 3 times. let it soak for a day, then replant. it decomposes old roots and stuff, then turns it into nutrients
PK 13/14: - Tends to be best used in a 7 - 10 day window starting about the time you see first flower formation. This typically, on an 8 week flower response group, to be about 5 weeks before harvest or 2-3 weeks after flower initiation (not light change). Adding it early will not advance or benefit flower initiation, only the amount of dark the plant sees will initiation flowering. Adding too early could result in phosphate accumulation and ratio issues involving Ca and Mg. If using A/B at full strength, cut it back a little as you introduce the PK. The best way to dial in the PK takes some trial and error work. This can be anything from 3 - 10 days after switching light cycle or the natural trigger for flower is received by the plant. Remember a plant has to convert to flower in most cases which takes a little time from the moment the dark cycle increases or decreases based on the species of plant being grown. Use PK for about a 3 week window at each irrigation along with the other components. Then you can stop. You really can not use PK too long except in the final week or so, or giving it too early. You want to use it when the buds are forming and just starting to kind of wrap around the branch (right before they start linking together)
Nutrient schedule for seedlings: - 1ml a+b and 1 mil rhizo - go a bit higher with every watering till you get to the normal chart level. PH to 5.2-6.2 (5.8 is a safe spot). Canna nutrient chart:
http://www.cannagardening.com/growguide
Nutrient schedule for clones: - Start with 8ml (each A/B bottle) per gallon and if there is no sight of burn, quickly move up to 10-12 ml per gallon. PH to 5.2-6.2 (5.8 is a safe spot). Use solution within 4 days.
Nutrient Mix Order: - Cal/Mag (if using), then Rhizotonic, then A/B etc.. - let sit for a couple hours or overnight if possible. Then adjust PH to 5.2-6.2 (5.8 is a good middle) and use it. Always add anything with Calcium first. Probably no need for cal mag until flowering if using non RO (city) water. If you use any product with silica in it then it should be added to your feed water before adding other nutes or you'll get nutrient lockout/dropout in the mix.
Watering: - Never use just plain water with coco. Use the A/B with EVERY watering except during the final flush. During the flush, just use Cannazym. If you want to reuse the coco (up to 3 times), then use a double dose of Cannazym during the flush. After plant removal, soak coco in double dose cannazym once more and let it soak for 24 hours, then it's ready to re-use. Re-using canna coco is good because the micro life gets built up from the previous grow.
PH: - Stay between 5.2 and 6.2. 5.8 is a good safe spot
Magnesium deficiencies: - Show as yellowing in-between the veins on the leaf and sometimes rust spots
Calcium deficiencies: - Show as brown edges on the sides of the leaves, and eventually twist and curl up and die. Calcium is important for cell density. A steady supply will increase yields.