OLD HEAD Photo x Gelato Auto

It looks like you are having a root issue. If the medium has been kept too wet then this can cause a lack of oxygen and allow root rot to set it. I would give them a dose of 2 tsp per gallon of 3% hydrogen peroxide and that should kill any bad bacteria that is killing the roots. Then let the pot dry out pretty well between waterings and make sure you have good drainage. Plants have a hard time recovering from major root damage, but hopefully you can get it turned around. Good luck!

What is the ph and ppm of your water before adding lemon. If its in our not far from the 5.8-6.9 range then don't add lemon. The soil will buffer. Do you check your soil ph before grow? This is something I learned to do in my early grows. Some soil can be very alkaline like 7-9 and needs adjusting to bring this down.