I think it's okay to give your pH a little play room as long as you are checking it regularly. A small drift is completely natural. Think about a plant growing in the ground. There is no way that plant is being kept at the "correct" pH yet she's still going to thrive if taken care of. You can't attribute "an increase in crystals" to a pH change of .3 over only a couple of days. She is growing, of course she'll fatten up as she ages and will pack on the most weight in the last couple of weeks.
I guess the point I'm trying to make is... if your plants look happy, healthy, and perky don't be so quick to nitpick your pH.
"And though we'd eliminated the threat of the enemy flying planes into buildings, no-one was prepared for terrorists flying two buildings into the sides of planes. No-one was killed but a lot of people were surprised." -Time Trumpet, Episode 3