PO4 test kits - Hanna VS Salifert

[GoFish]

Well this is slightly embarrassing. I just checked the Salifert PO4 kit and it expired in 08.16... could swear I checked all 4 boxes before Boxing Day And they were all good from 2018-2020 but for some reason had 2 Alk kits together and the PO4 was on a different shelf

Anyway, pointless technical thread question with an expired kit

However I may have an isssue...
Just did 2 back to back tests with the Hanna and got 125ppb (.38ppm) and then 114ppb (.35ppm). Might be more inaccurate than it's suppose to be. Instructions say within ±5 ppb ±5% of reading. It was 23ppb (.07) last night! Will need to do some research into this. The Salifert still shows much lower (but it's expired, interesting to know anyways)