can i get one of those kits at walmart or something and how much would something cheap for the ph cost?

dude im new to this stuff completely

and whats
"when your nutrient mixture doesn't fall within a range of 6.3-6.8 in soil" mean?

thanks

i also forgot to add that one night i woke up and ALL my leaves had like a gloss to them almost looked like someone sprayed clear glue on them and it dried. its only in little spots now and is slowly going away. i have no idea what that was. maybe it was some type of mold your talking about?