well if I have 5.8 or less and want 6.5 and then my way of thinking would be add 7.0 water which won't hurt your soil plants anyway...and take a readingyour new reading in my estimation should be 3-5 points higher than before add up/down accordingly to get to 6.5...or you can split the difference. i.e.you want 6.5 and your getting well under 6...let's make that # 5.8 for this example. since 5.8 is -.7 below desired ph...then add mix ph at +.7 or 7.2...the best way to know for sure in the future is to go for it...one way or the other, and learn.
another note is that too much water can lead to yellow leaves eventually, after they droop...but you should've noticed this...try feeding your plants equal n p k for a week and see if the new growth starts greening up...the old growth probalbly will not come back and watch for it to fall off...