Please help

So I am just about to flower and I check my ph and it reads 5.0 so I add some lime and it has not moved at all. I am growing in fox farm soil strain cherry alien. Plants been doing fine than all of a sudden I notice oh dropped big time. Now my ph meter only cost me 20 bucks it's not a very good one . I am wondering if it's my meter . When I use on my vegetables it has different reading. So thinking its my soil. Just not making sense to me at all . It was reading 6.4 for the longest and than 5.0-5.4 notice a little purple in younger stems to. Help me please

If the plant is doing fine, you shouldn't have to do anything. I'm growing in FFOF and FFHF along with a mix of coco, Alaskan humus, and perlite...I have not once checked my phone. Havent found a need to.

always a good idea to have ph drops at the ready,,i have 3 ph pens ,2 blue lab pens,,they arent fool proff,,if plants are doing fine,le them rock,in soil i never ph anyway ,coco i do,,keep your ppm and ec good and you good to go friend,,those cheap ph drops only 15 bucks and last long time if you insist on phing