PH HELP PLZZZZZ

I think its my ph its around 6. But my plants have droopy yellow leaves with some light brown spots on some. Is this overwatering or PH malfunction.The temp at night is usually like 72 in the day its like 87. Please help i will put pics on later but i have some of the same size plants in a plastic bin that dont even have ventilation and they are NOT doing this they are fine. They have the same soil and get the same water i water like once a day. But only the ones in my big grow box(refer to my other threads for pics.)are doing it ....any help i am much geatful for..thanks

drooping leaves are usually from over/under-watering but the spots could very well be from high ph level but you won't know without testing it. the kits i use are under ten bucks (the color coded one, similar to pool testers) and work great! a definite must-have for all indoor growers...