Question about dry rock

Hello everyone! I have a new 55 gallon set up with a 10 gallon sump. I currently have about 30 lbs of sand and 40 lbs of base rock in the DT. I also have about 3 lbs of crushed coral in my sump. I am on week 3 of my cycle. I've gone thru my ammonia spike and the levels currently registers near 0. I'm on the tail end of my nitrite spike (hopefully). And I'm starting to see small amounts of nitrate readings.



My question is this: I wanted to add another 20 lbs or so of base rock. Is it safe to add now while the tank is cycling or should I wait until my tank finishes cycling?



Also, once I see my nitrate spike, is it safe to add some chaeto in my sump?



Thanks in advance for any and all help!