4 Automatic strains in 1 flat 30l bucket

Green Gelato: 6.01.2021 will be 12 Weeks exact White Widow: 9.01.2021 will be 12 Weeks exact AK-420: 9 Weeks Purple Queen: 7 Weeks Water is the same. I had for some days EC over 2.4. This is why I have have some tipburns on the leaves all. I managed not and brought it to 2.0. But some liter water out and put some RO Water in. White Widow still droopy and the buds wont get bigger. They still look so immature. Seedbag died. It was also very droppy for soem days then I thoght root rot and put some 3% H2O2 into the water only 50ml into 3 litre water for some minutes then poured all water out washed the roots with tap water cleaned the pot with h2o2 and renewed the nutrietientswater. Since then it died. Dont know why.