Help With PH levels With My Fert Plz

So I am growing outdoors in 10 Liter pots with sunshine mix 4 and some worm castings. They Are about a month and a half old now and the weather started to get nicer finally and decided to give them BioThrive and cal mag once every four days. Did that for about 2 weeks then noticed leaves were turning yellow and brown. So I flushed them out and didnt give them the ferts for about 10 days. Then I checked my ph level of my water and ferts when together and its 4. What can I do to make it around 6.5 - 7? change from biothrive ? or can I add something to mix with the biothrive? Thanks

are you using tap? i use tap water that ranges from 7.5 to 8.5 and I have never had problems. But i use miracle gro.

I may be confused about what your asking but I dont think so but anyway you say your PH is 4.0 with your water and ferts togetherthats perfectly normal. Please forgive me when I say this because I'm not trying to make you feel dumb about this at all, but you are supposed to mix your water and ferts together and then check the PH (like you did) and then add your PH up or your PH down. Like I said, I may have been mistaken in what your asking. If i did then I am very sorry.
Also adding Dolomite lime to your soil helps the ph tremendously......1/2 TBL for every gallon of soil.

A couple ph up's you could try are silica product or humic acid product first mixed into your solution

bi carbonate of soda brings ph up just add a little to your feed then check the ph if it's to low add a little more then check.keep doing it until you get the ph you desire

after you mix your nutes.test then wait a while and test again..to me every 4 days seems a little much...

if you dont have any ph up or anything else then just add more water untill you reach a safe ph...

Thank u for the replies I will go and buy a ph up then !