Mixing h202 with nutes?

Just wondering how much hydrogen peroxide is safe to add when mixing nutrients? The chart I follow says 2.5ml per gallon. I’m using flora trio + cal mag with no other additives.
Do I adjust the pH before or after adding h202?

Always add ph up or down after nutrients are mixed with water, never combined nutrients without water I always fill a gal but leave room for nutrients

I have several gnats which didn't bother me until I found a dead gnat stuck to a pistil. I recently acquired some hp sauce and online sauces say 1 part hp to 4 part water but I'm like 'how do I calculate 1 part hp to 1 part water when it takes about a litre more or less to fully saturate the soil', 250ml to 1 litre sounds a bit much plus I'm in flower, send nudes, I mean how many pounds, I mean heylp