Help! I got another problem after a previous problem!

I am in deep water culture with clay peletes and an air rock with an air pump, using a 400 watt hps light and technaflora recipe for success for nutes but I ran out of the thrive alive b1 that's included in the kit so I bought blast off b1 as a substitute. I use a grow tent for the flowering. which the plants are 3 weeks into flowering. There are 4 plants in one setup I flowered them at about a foot tall. I had a problem before where the leaves were curling under and looked like they were slowly dying and a few of the top leaves were curling up but some of both tips turned brown and felt burnt so I raised my light just to see if it would help but didn't seem like it. I also got a tip to add hydrogen peroxide to my reservoir to kill any bacteria, bugs ect. So I did and it looks like for the most part the curling stopped but now there is a new problem. I added the same amount of nutes to a new water mix that I usually do after the hydrogen peroxide mix and now some of the leaves are turning yellow on the edges and then brownish. I'm assuming the plants got a bit of a shock from the problem that occurred the first time and are still recovering but some of the buds on one of the plants, the hairs turned a brownish orange. All of them. At this point some new white hairs are coming in after a few days of recovery that's why I think the plants got some what of a shock. I just don't know what to do about the leaves turning yellow/brown on the other plants. I mean the buds are growing perfectly fine on the plants with the yellowing/browning leaves but those plants did not get effected by the curling problem. The plants with the brownish/orange hairs on the buds are the ones effected from the curling of leaves and it seems like the buds are just now starting to grow again after a few days of recovery. Can anyone help me the the yellowing/browning of leaves? I don't know what to do. ​

Sounds like you over fed the plants when you did the res change? PH and E.C need to be checked.

Yea I checked the ph and it was 7.2 I got it down to 5.8 and it looks like the plants are bouncing back a little bit but it still seems like there is some what of a problem. the buds are getting bigger on 3 out of 4 plants the 4th one was the one that was hit the hardest with my first problem. I think it is still in some what of a shock but new white hairs are coming in so I think that the buds should start getting bigger soon on it. I don't know what E.C is or how to check it. Could you explain please?

Ec refers to ppm. The amount of nutes in water. Check out my journal entry for ppm guide lines. Keep in mind journal entry is in .5, ec is universal though.