You have very beautiful and branched plants. I'm sorry to see the suffering one, but I think that as long as it is limited to the lower leaves, it can be recovered without major problems, you just need to understand what deficiency it has. Sometimes it's the PH, because some individual plants absorb at slightly different PHs.

I use a PH of 6.5/7 but sometimes one or two plants would have these problems and I would try a PH of 8 and they would start to reabsorb properly.

I wish you the best growth :).