I am mixing my own solutions for both.
I use stump removal for no3 https://www.lowes.com/pd/Spectracide-16-oz-Stump-Remover/4764059?cm_mmc=shp-_-c-_-prd-_-lwn-_-google-_-lia-_-241-_-grassandweedchemicals-_-4764059-_-0&placeholder=null&ds_rl=1286981&gclid=CjwKCAiAuoqABhAsEiwAdSkVVOZA02bc8KNFvGnJzvJHkErTqsZ7t9yiQvl0T8jolX5iAUdb2vBn2xoCPdwQAvD_BwE&gclsrc=aw.ds
and trisodium phosphate for po4
Trisodium Phosphate [Na3O4P] 99.9% ACS Grade Crystals 8 Oz in a Space-Saver Bottle USA https://www.amazon.com/dp/B00WSKKTZ6/ref=cm_sw_r_cp_api_glc_fabc_SHZaGb008TN9Z?_encoding=UTF8&psc=1