Roots should be white and not stuck together like mushed together. Reservoir should not smell bad. If any of those signs could be root rot aka the dreaded pythium. Yellowing leaves can mean lack of nitrogen or possibly leaf septoria like mentioned above. If it had root rot it will droop like that and die off if not fixed fast. Hydroguard can be a life saver for root rot or root problems. Also if that doesn't work you can brew a tea. Look up Heisenberg tea on Google. There's a good thread on RIU to brew beneficial bacteria tea to solve problems. Or be like me and use real growers recharge as a tea. Cheaper and working for me.
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