my dwc setup that needs advice

ok guys ill try to keep it short b/c huge walls of text suck!

i have a 12 gallon(only use 10) dwc res with two airstones, ph 5.8-6.5. My ppm meter needs batteries but im at about 1/2 a teaspoon per gallon(seems to be working ok). These plants are about a month old and have been through alot since my ph meter took forever to come in :/ but here they are about 4 days into flowering. Can someone please help me identify this problem im having with little brown spots on the end of the leaves that slowly progresses down the leaf until its dead??

the plants are biggest to smallest Shaman, strawberry blue, c99. and sry for how shitty these plants are so please dont hate on me i just want a little free bud to smoke so even a small yeild will do.

Those leaves are burned. Could be Calcium Magnesium deficiency ( if you are using R/O water you need Cal/Mag) or it could be nute burn since you didnt have a proper PPM meter.

thanks for the input man, i am using r/o water so i guess i need some cal/mag. do you know of what i could use in the meantime?

YOu need Cal/mag , reverse osmosis filters that shit out. Get some for future use. I heard you can try and use Epsom salt in place of Cal/ Mag.
I think what you have is nutrient burn. Check your PPM it's probably way too high, then dilute your reservoir by taking out a gallon of water and putting back in a fresh gallon of r/o water and check PPM again until you reach desired level.

got it thanks bro