Plant has turned yellow, please help!

I recently put 2 cuttings into pots and the one on the left in the attached image has turned yellow. I've since drained all the food and replaced it with fresh nutes.

The PH was low on this plant that turned yellow and was high on the one that stayed green.

Any ideas what's causing this poor girl to look so ill? and what can I do to help her?

Attachment 283716

I just kept feeding it as normal and it has now began to recover and turn green again. Growth was slowed and there are now yellow and brown patches on some of the effected leaves but new growth is ok