Mixed tent - Barney´s Farm- DutchPassion - Sweetseeds

After I repotted the plants, they grew really well and healthily for 12 days. Now they are showing iron deficiency again... I already had the problem before repotting. The pH value of the earth has fallen again to 4.8 to 5.7. This time I used biodegradable braids to germinate. I believe that this is the reason for the PH fluctuations in the soil. Every time I water I measure the PH and adjust it to 6 - 6.5. Nevertheless, the PH value drops back to 4 to 5. I'm trying to correct the problem. I also work with neemoil because I can't get rid of the trips