I use KNO3 as the main and the sole source for several years, never could tell any difference.
Adding K2SO4 will not hurt also in addition to KNO3.
the % from KH2PO4 is not that big of a deal really, GH booster also is 50% K2SO4, so adding that after a water change, and adding KNO3 tends to supply plenty(excess non limiting amount).
Few test K+, it's a fav to blame for stunted tips(falsified resoundly however), or holes in the leaves(sometimes the case if they do not dose any etc).
If you are adding it, it's unlikely that is the issue. You can add more via K2SO4 if you want to look at K+ independent of PO4 and NO3.
Many did this in the 1990's.
Does not harm anything, but you certainly do not need it.
See the sticky here also on K+.
Regards,
tom Barr