Return of the algae

Haven't been on lately pool has been good using BBB method.Having problem with algae returning after treating for it. Shocked pool last week, brushed and vaced and backwashed DE filter. It came back agian this week ,looks like mustard algae after seeing it on a post. The weather here in Ohio is getting cooler ,will be closing the pool soon.Want to make sure it is gone before closing. I use a Polyquat algaecide 60% weekly.I have been having trouble keeping the PH up,had to add lots more Borax to get it up.I brushed ,vaced and backwashed today.Also added anothe gallon of 10% chlorine.
Reading's today
chlorine 5.5
PH 7.2
TA 70
CH 150
SI -1.0
water temp 64
outside temp 54

What's your CYA level?

The CYA is 60,the chlorine is now at 9.0 and PH at 7.5 after additions. I'm using Taylor k 2006 kit.

In that case you'll want to take your FC to 20 or higher and do your best to keep it above 20 until you can go from sundown until sunup without losing more than .5ppm FC. Here's the chart and page that explains the calculation: http://poolsolutions.com/gd/best-gue...e-chart.html#a

Also, run your pump/filter 24x7 until you're finished.

Thanks for your help,algae gone ,water clear and bright. To bad the season is bout over here.I can see where I need to keep the chlorine level higher during the season. Most likely would not have had the algae problem with the higher level. I will use the suggested chart a reference.I'm also going to split the pump cycle to run twice a day. To all those with algae problems ,don't let the chlorine level drop to low! Thanks again.