I wrote the owner of the company that makes Gravity, Bushmasters, Purple Maxx, Snow Storm about using their products in pure Coco medium...
This is his response:
We have had reports of people having burning when using BushMaster or Gravity with coco. However, those people were using a flood and drain with nutes that were not optimized for coco. Its been a long time since weve heard of any problems. Also, strains have changed over time so the problem may have been certain strain related. If youre interested in experimenting with a few plants you could try using Gravity at the rate of ½ to 1 ml. per gallon every other day for two or three feedings and see if theres any burning. If not then you could continue until theyve had about5 feedings. The Purple Maxx and the Snow Storm Ultra both work well in any medium.
If you do decide to experiment with the Gravity or Bushmasters in Coco, please let me know what happens, whether good or bad. We count on customer feedback to help us develop and improve our products.
Thanks, Phil (owner)