It should be fine, but I find that KH2PO4 and KNO3 dissolve quickly in a mug of tank water (normal 20-40g EI dose) ...5-10 mins anyway. CSM+B takes closer to 30 mins. Either way, every morning I scoop up a mug of water, measure out the chems (alternating macros and micros), and let it sit for a while. I come back later, give it a final stir, and dump. That way I don't have to make a trip to the kitchen.