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i water when the soil is dry plus i check with a three way thingy that check the wetness of the soil its ph and the light
don't just depend on a "thingy" for any of your measurements.
You need to know the PH level by numbers. not just what an idiot box tells you.
You should also know the TDS level when you feed.
With little but this pic to go on it looks under watered and could use more feed.
You also do not mention lighting.
You provide little to work with.
start by knowing the PH of your water. Get control of your feed schedule and beef up your lights.
just by the pic it looks like you could use some adjustments there too.
Best of luck to you and Happy Growing.