Lemon Juice!! For Ph Down

i heard that you could use lemon juice for down and vinegar for up. my question is..... are there any negatives to using these household products?

Yes they both will lower your ph.....they are both acid.
Baking soda will raise ph in a pinch.

Neither of those is made for your system and neither has any ph buffers to keep your ph stable. A small amount is probably harmless enough but I have no idea about a large amount.