I have heard of people using some of the products in the pure blend line of products with blumats but I would be to paranoid it was going to clog. The living soil works perfect with them so I don't have to mess around with the water.
If you use any products in the res you have to agitate the water to keep it mixed up, that usually creates bubbles which is a nemesis to the blumat lines, so not only could the stuff your adding to the res clog the lines, you could create a big air bubble in your line fucking up one of your blumats.
Lots of people do it, but I personally steer clear of it just to be safe